Merge branch 'jk/skip-prefix'

* jk/skip-prefix:
  http-push: refactor parsing of remote object names
  imap-send: use skip_prefix instead of using magic numbers
  use skip_prefix to avoid repeated calculations
  git: avoid magic number with skip_prefix
  fetch-pack: refactor parsing in get_ack
  fast-import: refactor parsing of spaces
  stat_opt: check extra strlen call
  daemon: use skip_prefix to avoid magic numbers
  fast-import: use skip_prefix for parsing input
  use skip_prefix to avoid repeating strings
  use skip_prefix to avoid magic numbers
  transport-helper: avoid reading past end-of-string
  fast-import: fix read of uninitialized argv memory
  apply: use skip_prefix instead of raw addition
  refactor skip_prefix to return a boolean
  avoid using skip_prefix as a boolean
  daemon: mark some strings as const
  parse_diff_color_slot: drop ofs parameter

40 files changed, 407 insertions, 401 deletions

diff --git a/advice.c b/advice.c
index c50ebdf5fe..9b42033192 100644
--- a/advice.c
+++ b/advice.c
@@ -61,9 +61,12 @@ void advise(const char *advice, ...)
 
 int git_default_advice_config(const char *var, const char *value)
 {
-	const char *k = skip_prefix(var, "advice.");
+	const char *k;
 	int i;
 
+	if (!skip_prefix(var, "advice.", &k))
+		return 0;
+
 	for (i = 0; i < ARRAY_SIZE(advice_config); i++) {
 		if (strcmp(k, advice_config[i].name))
 			continue;
diff --git a/alias.c b/alias.c
index 5efc3d6986..758c867149 100644
--- a/alias.c
+++ b/alias.c
@@ -5,7 +5,8 @@ static char *alias_val;
 
 static int alias_lookup_cb(const char *k, const char *v, void *cb)
 {
-	if (starts_with(k, "alias.") && !strcmp(k + 6, alias_key)) {
+	const char *name;
+	if (skip_prefix(k, "alias.", &name) && !strcmp(name, alias_key)) {
 		if (!v)
 			return config_error_nonbool(k);
 		alias_val = xstrdup(v);
diff --git a/branch.c b/branch.c
index 660097bc29..46e8aa86df 100644
--- a/branch.c
+++ b/branch.c
@@ -50,11 +50,11 @@ static int should_setup_rebase(const char *origin)
 
 void install_branch_config(int flag, const char *local, const char *origin, const char *remote)
 {
-	const char *shortname = skip_prefix(remote, "refs/heads/");
+	const char *shortname = NULL;
 	struct strbuf key = STRBUF_INIT;
 	int rebasing = should_setup_rebase(origin);
 
-	if (shortname
+	if (skip_prefix(remote, "refs/heads/", &shortname)
 	    && !strcmp(local, shortname)
 	    && !origin) {
 		warning(_("Not setting branch %s as its own upstream."),
diff --git a/builtin/apply.c b/builtin/apply.c
index 9c5724eacc..bc924ab2d0 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3847,9 +3847,10 @@ static void add_index_file(const char *path, unsigned mode, void *buf, unsigned
 	ce->ce_flags = create_ce_flags(0);
 	ce->ce_namelen = namelen;
 	if (S_ISGITLINK(mode)) {
-		const char *s = buf;
+		const char *s;
 
-		if (get_sha1_hex(s + strlen("Subproject commit "), ce->sha1))
+		if (!skip_prefix(buf, "Subproject commit ", &s) ||
+		    get_sha1_hex(s, ce->sha1))
 			die(_("corrupt patch for submodule %s"), path);
 	} else {
 		if (!cached) {
diff --git a/builtin/branch.c b/builtin/branch.c
index 652b1d2d14..0591b22a48 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -294,13 +294,13 @@ static char *resolve_symref(const char *src, const char *prefix)
 {
 	unsigned char sha1[20];
 	int flag;
-	const char *dst, *cp;
+	const char *dst;
 
 	dst = resolve_ref_unsafe(src, sha1, 0, &flag);
 	if (!(dst && (flag & REF_ISSYMREF)))
 		return NULL;
-	if (prefix && (cp = skip_prefix(dst, prefix)))
-		dst = cp;
+	if (prefix)
+		skip_prefix(dst, prefix, &dst);
 	return xstrdup(dst);
 }
 
diff --git a/builtin/checkout.c b/builtin/checkout.c
index f1dc56e55f..463cfeea50 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -776,8 +776,8 @@ static int switch_branches(const struct checkout_opts *opts,
 	if (!(flag & REF_ISSYMREF))
 		old.path = NULL;
 
-	if (old.path && starts_with(old.path, "refs/heads/"))
-		old.name = old.path + strlen("refs/heads/");
+	if (old.path)
+		skip_prefix(old.path, "refs/heads/", &old.name);
 
 	if (!new->name) {
 		new->name = "HEAD";
diff --git a/builtin/clone.c b/builtin/clone.c
index b12989d1ca..a5b2d9db36 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -584,11 +584,11 @@ static void update_remote_refs(const struct ref *refs,
 static void update_head(const struct ref *our, const struct ref *remote,
 			const char *msg)
 {
-	if (our && starts_with(our->name, "refs/heads/")) {
+	const char *head;
+	if (our && skip_prefix(our->name, "refs/heads/", &head)) {
 		/* Local default branch link */
 		create_symref("HEAD", our->name, NULL);
 		if (!option_bare) {
-			const char *head = skip_prefix(our->name, "refs/heads/");
 			update_ref(msg, "HEAD", our->old_sha1, NULL, 0,
 				   UPDATE_REFS_DIE_ON_ERR);
 			install_branch_config(0, head, option_origin, our->name);
@@ -703,9 +703,12 @@ static void write_refspec_config(const char* src_ref_prefix,
 					strbuf_addf(&value, "+%s:%s%s", our_head_points_at->name,
 						branch_top->buf, option_branch);
 			} else if (remote_head_points_at) {
+				const char *head = remote_head_points_at->name;
+				if (!skip_prefix(head, "refs/heads/", &head))
+					die("BUG: remote HEAD points at non-head?");
+
 				strbuf_addf(&value, "+%s:%s%s", remote_head_points_at->name,
-						branch_top->buf,
-						skip_prefix(remote_head_points_at->name, "refs/heads/"));
+						branch_top->buf, head);
 			}
 			/*
 			 * otherwise, the next "git fetch" will
diff --git a/builtin/commit.c b/builtin/commit.c
index 84cec9a715..461c3b1cad 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1020,7 +1020,7 @@ static int message_is_empty(struct strbuf *sb)
 static int template_untouched(struct strbuf *sb)
 {
 	struct strbuf tmpl = STRBUF_INIT;
-	char *start;
+	const char *start;
 
 	if (cleanup_mode == CLEANUP_NONE && sb->len)
 		return 0;
@@ -1029,8 +1029,7 @@ static int template_untouched(struct strbuf *sb)
 		return 0;
 
 	stripspace(&tmpl, cleanup_mode == CLEANUP_ALL);
-	start = (char *)skip_prefix(sb->buf, tmpl.buf);
-	if (!start)
+	if (!skip_prefix(sb->buf, tmpl.buf, &start))
 		start = sb->buf;
 	strbuf_release(&tmpl);
 	return rest_is_empty(sb, start - sb->buf);
diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index ef8b254ef2..971e802c6f 100644
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -100,7 +100,8 @@ static int handle_line(char *line, struct merge_parents *merge_parents)
 {
 	int i, len = strlen(line);
 	struct origin_data *origin_data;
-	char *src, *origin;
+	char *src;
+	const char *origin;
 	struct src_data *src_data;
 	struct string_list_item *item;
 	int pulling_head = 0;
@@ -164,8 +165,7 @@ static int handle_line(char *line, struct merge_parents *merge_parents)
 		origin = line;
 		string_list_append(&src_data->tag, origin + 4);
 		src_data->head_status |= 2;
-	} else if (starts_with(line, "remote-tracking branch ")) {
-		origin = line + strlen("remote-tracking branch ");
+	} else if (skip_prefix(line, "remote-tracking branch ", &origin)) {
 		string_list_append(&src_data->r_branch, origin);
 		src_data->head_status |= 2;
 	} else {
@@ -300,8 +300,8 @@ static void credit_people(struct strbuf *out,
 	if (!them->nr ||
 	    (them->nr == 1 &&
 	     me &&
-	     (me = skip_prefix(me, them->items->string)) != NULL &&
-	     skip_prefix(me, " <")))
+	     skip_prefix(me, them->items->string, &me) &&
+	     starts_with(me, " <")))
 		return;
 	strbuf_addf(out, "\n%c %s ", comment_line_char, label);
 	add_people_count(out, them);
diff --git a/builtin/log.c b/builtin/log.c
index 92063dfc48..27c1b65db4 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -871,7 +871,7 @@ static char *find_branch_name(struct rev_info *rev)
 	int i, positive = -1;
 	unsigned char branch_sha1[20];
 	const unsigned char *tip_sha1;
-	const char *ref;
+	const char *ref, *v;
 	char *full_ref, *branch = NULL;
 
 	for (i = 0; i < rev->cmdline.nr; i++) {
@@ -887,9 +887,9 @@ static char *find_branch_name(struct rev_info *rev)
 	ref = rev->cmdline.rev[positive].name;
 	tip_sha1 = rev->cmdline.rev[positive].item->sha1;
 	if (dwim_ref(ref, strlen(ref), branch_sha1, &full_ref) &&
-	    starts_with(full_ref, "refs/heads/") &&
+	    skip_prefix(full_ref, "refs/heads/", &v) &&
 	    !hashcmp(tip_sha1, branch_sha1))
-		branch = xstrdup(full_ref + strlen("refs/heads/"));
+		branch = xstrdup(v);
 	free(full_ref);
 	return branch;
 }
@@ -1396,10 +1396,10 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 
 		if (check_head) {
 			unsigned char sha1[20];
-			const char *ref;
+			const char *ref, *v;
 			ref = resolve_ref_unsafe("HEAD", sha1, 1, NULL);
-			if (ref && starts_with(ref, "refs/heads/"))
-				branch_name = xstrdup(ref + strlen("refs/heads/"));
+			if (ref && skip_prefix(ref, "refs/heads/", &v))
+				branch_name = xstrdup(v);
 			else
 				branch_name = xstrdup(""); /* no branch */
 		}
diff --git a/builtin/push.c b/builtin/push.c
index f8dfea41e1..f50e3d5e77 100644
--- a/builtin/push.c
+++ b/builtin/push.c
@@ -127,11 +127,10 @@ static NORETURN int die_push_simple(struct branch *branch, struct remote *remote
 	 * them the big ugly fully qualified ref.
 	 */
 	const char *advice_maybe = "";
-	const char *short_upstream =
-		skip_prefix(branch->merge[0]->src, "refs/heads/");
+	const char *short_upstream = branch->merge[0]->src;
+
+	skip_prefix(short_upstream, "refs/heads/", &short_upstream);
 
-	if (!short_upstream)
-		short_upstream = branch->merge[0]->src;
 	/*
 	 * Don't show advice for people who explicitly set
 	 * push.default.
diff --git a/builtin/remote.c b/builtin/remote.c
index c9102e8fe9..a8efe3da4d 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -250,9 +250,7 @@ static struct string_list branch_list;
 
 static const char *abbrev_ref(const char *name, const char *prefix)
 {
-	const char *abbrev = skip_prefix(name, prefix);
-	if (abbrev)
-		return abbrev;
+	skip_prefix(name, prefix, &name);
 	return name;
 }
 #define abbrev_branch(name) abbrev_ref((name), "refs/heads/")
diff --git a/column.c b/column.c
index 1a468debb4..ca878bcea7 100644
--- a/column.c
+++ b/column.c
@@ -336,8 +336,9 @@ static int column_config(const char *var, const char *value,
 int git_column_config(const char *var, const char *value,
 		      const char *command, unsigned int *colopts)
 {
-	const char *it = skip_prefix(var, "column.");
-	if (!it)
+	const char *it;
+
+	if (!skip_prefix(var, "column.", &it))
 		return 0;
 
 	if (!strcmp(it, "ui"))
diff --git a/commit.c b/commit.c
index 4ff8077dbf..fb7897c2a4 100644
--- a/commit.c
+++ b/commit.c
@@ -614,8 +614,7 @@ static void record_author_date(struct author_date_slab *author_date,
 
 	for (buf = buffer; buf; buf = line_end + 1) {
 		line_end = strchrnul(buf, '\n');
-		ident_line = skip_prefix(buf, "author ");
-		if (!ident_line) {
+		if (!skip_prefix(buf, "author ", &ident_line)) {
 			if (!line_end[0] || line_end[1] == '\n')
 				return; /* end of header */
 			continue;
@@ -1237,8 +1236,7 @@ static void parse_gpg_output(struct signature_check *sigc)
 	for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
 		const char *found, *next;
 
-		found = skip_prefix(buf, sigcheck_gpg_status[i].check + 1);
-		if (!found) {
+		if (!skip_prefix(buf, sigcheck_gpg_status[i].check + 1, &found)) {
 			found = strstr(buf, sigcheck_gpg_status[i].check);
 			if (!found)
 				continue;
diff --git a/config.c b/config.c
index a1aef1cf3e..ba882a1f51 100644
--- a/config.c
+++ b/config.c
@@ -138,8 +138,7 @@ int git_config_include(const char *var, const char *value, void *data)
 	if (ret < 0)
 		return ret;
 
-	type = skip_prefix(var, "include.");
-	if (!type)
+	if (!skip_prefix(var, "include.", &type))
 		return ret;
 
 	if (!strcmp(type, "path"))
diff --git a/connect.c b/connect.c
index 94a6650246..37ff018f13 100644
--- a/connect.c
+++ b/connect.c
@@ -129,6 +129,7 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
 		char *name;
 		int len, name_len;
 		char *buffer = packet_buffer;
+		const char *arg;
 
 		len = packet_read(in, &src_buf, &src_len,
 				  packet_buffer, sizeof(packet_buffer),
@@ -140,12 +141,12 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
 		if (!len)
 			break;
 
-		if (len > 4 && starts_with(buffer, "ERR "))
-			die("remote error: %s", buffer + 4);
+		if (len > 4 && skip_prefix(buffer, "ERR ", &arg))
+			die("remote error: %s", arg);
 
-		if (len == 48 && starts_with(buffer, "shallow ")) {
-			if (get_sha1_hex(buffer + 8, old_sha1))
-				die("protocol error: expected shallow sha-1, got '%s'", buffer + 8);
+		if (len == 48 && skip_prefix(buffer, "shallow ", &arg)) {
+			if (get_sha1_hex(arg, old_sha1))
+				die("protocol error: expected shallow sha-1, got '%s'", arg);
 			if (!shallow_points)
 				die("repository on the other end cannot be shallow");
 			sha1_array_append(shallow_points, old_sha1);
diff --git a/convert.c b/convert.c
index ab80b72357..cb5fbb45ea 100644
--- a/convert.c
+++ b/convert.c
@@ -1121,9 +1121,9 @@ static int is_foreign_ident(const char *str)
 {
 	int i;
 
-	if (!starts_with(str, "$Id: "))
+	if (!skip_prefix(str, "$Id: ", &str))
 		return 0;
-	for (i = 5; str[i]; i++) {
+	for (i = 0; str[i]; i++) {
 		if (isspace(str[i]) && str[i+1] != '$')
 			return 1;
 	}
diff --git a/credential-cache--daemon.c b/credential-cache--daemon.c
index 390f194252..3b370ca5e5 100644
--- a/credential-cache--daemon.c
+++ b/credential-cache--daemon.c
@@ -109,14 +109,12 @@ static int read_request(FILE *fh, struct credential *c,
 	const char *p;
 
 	strbuf_getline(&item, fh, '\n');
-	p = skip_prefix(item.buf, "action=");
-	if (!p)
+	if (!skip_prefix(item.buf, "action=", &p))
 		return error("client sent bogus action line: %s", item.buf);
 	strbuf_addstr(action, p);
 
 	strbuf_getline(&item, fh, '\n');
-	p = skip_prefix(item.buf, "timeout=");
-	if (!p)
+	if (!skip_prefix(item.buf, "timeout=", &p))
 		return error("client sent bogus timeout line: %s", item.buf);
 	*timeout = atoi(p);
 
diff --git a/credential.c b/credential.c
index e54753c75d..4d79d320f8 100644
--- a/credential.c
+++ b/credential.c
@@ -40,8 +40,7 @@ static int credential_config_callback(const char *var, const char *value,
 	struct credential *c = data;
 	const char *key, *dot;
 
-	key = skip_prefix(var, "credential.");
-	if (!key)
+	if (!skip_prefix(var, "credential.", &key))
 		return 0;
 
 	if (!value)
diff --git a/daemon.c b/daemon.c
index f9c63e9613..1eb6631723 100644
--- a/daemon.c
+++ b/daemon.c
@@ -39,8 +39,8 @@ static int strict_paths;
 static int export_all_trees;
 
 /* Take all paths relative to this one if non-NULL */
-static char *base_path;
-static char *interpolated_path;
+static const char *base_path;
+static const char *interpolated_path;
 static int base_path_relaxed;
 
 /* Flag indicating client sent extra args. */
@@ -106,12 +106,12 @@ static void NORETURN daemon_die(const char *err, va_list params)
 	exit(1);
 }
 
-static const char *path_ok(char *directory)
+static const char *path_ok(const char *directory)
 {
 	static char rpath[PATH_MAX];
 	static char interp_path[PATH_MAX];
 	const char *path;
-	char *dir;
+	const char *dir;
 
 	dir = directory;
 
@@ -131,7 +131,7 @@ static const char *path_ok(char *directory)
 			 * "~alice/%s/foo".
 			 */
 			int namlen, restlen = strlen(dir);
-			char *slash = strchr(dir, '/');
+			const char *slash = strchr(dir, '/');
 			if (!slash)
 				slash = dir + restlen;
 			namlen = slash - dir;
@@ -235,8 +235,10 @@ static int service_enabled;
 
 static int git_daemon_config(const char *var, const char *value, void *cb)
 {
-	if (starts_with(var, "daemon.") &&
-	    !strcmp(var + 7, service_looking_at->config_name)) {
+	const char *service;
+
+	if (skip_prefix(var, "daemon.", &service) &&
+	    !strcmp(service, service_looking_at->config_name)) {
 		service_enabled = git_config_bool(var, value);
 		return 0;
 	}
@@ -253,7 +255,7 @@ static int daemon_error(const char *dir, const char *msg)
 	return -1;
 }
 
-static char *access_hook;
+static const char *access_hook;
 
 static int run_access_hook(struct daemon_service *service, const char *dir, const char *path)
 {
@@ -318,7 +320,7 @@ error_return:
 	return -1;
 }
 
-static int run_service(char *dir, struct daemon_service *service)
+static int run_service(const char *dir, struct daemon_service *service)
 {
 	const char *path;
 	int enabled = service->enabled;
@@ -624,15 +626,16 @@ static int execute(void)
 
 	for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
 		struct daemon_service *s = &(daemon_service[i]);
-		int namelen = strlen(s->name);
-		if (starts_with(line, "git-") &&
-		    !strncmp(s->name, line + 4, namelen) &&
-		    line[namelen + 4] == ' ') {
+		const char *arg;
+
+		if (skip_prefix(line, "git-", &arg) &&
+		    skip_prefix(arg, s->name, &arg) &&
+		    *arg++ == ' ') {
 			/*
 			 * Note: The directory here is probably context sensitive,
 			 * and might depend on the actual service being performed.
 			 */
-			return run_service(line + namelen + 5, s);
+			return run_service(arg, s);
 		}
 	}
 
@@ -1133,16 +1136,17 @@ int main(int argc, char **argv)
 
 	for (i = 1; i < argc; i++) {
 		char *arg = argv[i];
+		const char *v;
 
-		if (starts_with(arg, "--listen=")) {
-			string_list_append(&listen_addr, xstrdup_tolower(arg + 9));
+		if (skip_prefix(arg, "--listen=", &v)) {
+			string_list_append(&listen_addr, xstrdup_tolower(v));
 			continue;
 		}
-		if (starts_with(arg, "--port=")) {
+		if (skip_prefix(arg, "--port=", &v)) {
 			char *end;
 			unsigned long n;
-			n = strtoul(arg+7, &end, 0);
-			if (arg[7] && !*end) {
+			n = strtoul(v, &end, 0);
+			if (*v && !*end) {
 				listen_port = n;
 				continue;
 			}
@@ -1168,20 +1172,20 @@ int main(int argc, char **argv)
 			export_all_trees = 1;
 			continue;
 		}
-		if (starts_with(arg, "--access-hook=")) {
-			access_hook = arg + 14;
+		if (skip_prefix(arg, "--access-hook=", &v)) {
+			access_hook = v;
 			continue;
 		}
-		if (starts_with(arg, "--timeout=")) {
-			timeout = atoi(arg+10);
+		if (skip_prefix(arg, "--timeout=", &v)) {
+			timeout = atoi(v);
 			continue;
 		}
-		if (starts_with(arg, "--init-timeout=")) {
-			init_timeout = atoi(arg+15);
+		if (skip_prefix(arg, "--init-timeout=", &v)) {
+			init_timeout = atoi(v);
 			continue;
 		}
-		if (starts_with(arg, "--max-connections=")) {
-			max_connections = atoi(arg+18);
+		if (skip_prefix(arg, "--max-connections=", &v)) {
+			max_connections = atoi(v);
 			if (max_connections < 0)
 				max_connections = 0;	        /* unlimited */
 			continue;
@@ -1190,16 +1194,16 @@ int main(int argc, char **argv)
 			strict_paths = 1;
 			continue;
 		}
-		if (starts_with(arg, "--base-path=")) {
-			base_path = arg+12;
+		if (skip_prefix(arg, "--base-path=", &v)) {
+			base_path = v;
 			continue;
 		}
 		if (!strcmp(arg, "--base-path-relaxed")) {
 			base_path_relaxed = 1;
 			continue;
 		}
-		if (starts_with(arg, "--interpolated-path=")) {
-			interpolated_path = arg+20;
+		if (skip_prefix(arg, "--interpolated-path=", &v)) {
+			interpolated_path = v;
 			continue;
 		}
 		if (!strcmp(arg, "--reuseaddr")) {
@@ -1210,12 +1214,12 @@ int main(int argc, char **argv)
 			user_path = "";
 			continue;
 		}
-		if (starts_with(arg, "--user-path=")) {
-			user_path = arg + 12;
+		if (skip_prefix(arg, "--user-path=", &v)) {
+			user_path = v;
 			continue;
 		}
-		if (starts_with(arg, "--pid-file=")) {
-			pid_file = arg + 11;
+		if (skip_prefix(arg, "--pid-file=", &v)) {
+			pid_file = v;
 			continue;
 		}
 		if (!strcmp(arg, "--detach")) {
@@ -1223,28 +1227,28 @@ int main(int argc, char **argv)
 			log_syslog = 1;
 			continue;
 		}
-		if (starts_with(arg, "--user=")) {
-			user_name = arg + 7;
+		if (skip_prefix(arg, "--user=", &v)) {
+			user_name = v;
 			continue;
 		}
-		if (starts_with(arg, "--group=")) {
-			group_name = arg + 8;
+		if (skip_prefix(arg, "--group=", &v)) {
+			group_name = v;
 			continue;
 		}
-		if (starts_with(arg, "--enable=")) {
-			enable_service(arg + 9, 1);
+		if (skip_prefix(arg, "--enable=", &v)) {
+			enable_service(v, 1);
 			continue;
 		}
-		if (starts_with(arg, "--disable=")) {
-			enable_service(arg + 10, 0);
+		if (skip_prefix(arg, "--disable=", &v)) {
+			enable_service(v, 0);
 			continue;
 		}
-		if (starts_with(arg, "--allow-override=")) {
-			make_service_overridable(arg + 17, 1);
+		if (skip_prefix(arg, "--allow-override=", &v)) {
+			make_service_overridable(v, 1);
 			continue;
 		}
-		if (starts_with(arg, "--forbid-override=")) {
-			make_service_overridable(arg + 18, 0);
+		if (skip_prefix(arg, "--forbid-override=", &v)) {
+			make_service_overridable(v, 0);
 			continue;
 		}
 		if (!strcmp(arg, "--informative-errors")) {
diff --git a/diff.c b/diff.c
index bba9a558a6..06bdfb8ae5 100644
--- a/diff.c
+++ b/diff.c
@@ -52,23 +52,23 @@ static char diff_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_NORMAL,	/* FUNCINFO */
 };
 
-static int parse_diff_color_slot(const char *var, int ofs)
+static int parse_diff_color_slot(const char *var)
 {
-	if (!strcasecmp(var+ofs, "plain"))
+	if (!strcasecmp(var, "plain"))
 		return DIFF_PLAIN;
-	if (!strcasecmp(var+ofs, "meta"))
+	if (!strcasecmp(var, "meta"))
 		return DIFF_METAINFO;
-	if (!strcasecmp(var+ofs, "frag"))
+	if (!strcasecmp(var, "frag"))
 		return DIFF_FRAGINFO;
-	if (!strcasecmp(var+ofs, "old"))
+	if (!strcasecmp(var, "old"))
 		return DIFF_FILE_OLD;
-	if (!strcasecmp(var+ofs, "new"))
+	if (!strcasecmp(var, "new"))
 		return DIFF_FILE_NEW;
-	if (!strcasecmp(var+ofs, "commit"))
+	if (!strcasecmp(var, "commit"))
 		return DIFF_COMMIT;
-	if (!strcasecmp(var+ofs, "whitespace"))
+	if (!strcasecmp(var, "whitespace"))
 		return DIFF_WHITESPACE;
-	if (!strcasecmp(var+ofs, "func"))
+	if (!strcasecmp(var, "func"))
 		return DIFF_FUNCINFO;
 	return -1;
 }
@@ -231,6 +231,8 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 
 int git_diff_basic_config(const char *var, const char *value, void *cb)
 {
+	const char *name;
+
 	if (!strcmp(var, "diff.renamelimit")) {
 		diff_rename_limit_default = git_config_int(var, value);
 		return 0;
@@ -239,8 +241,9 @@ int git_diff_basic_config(const char *var, const char *value, void *cb)
 	if (userdiff_config(var, value) < 0)
 		return -1;
 
-	if (starts_with(var, "diff.color.") || starts_with(var, "color.diff.")) {
-		int slot = parse_diff_color_slot(var, 11);
+	if (skip_prefix(var, "diff.color.", &name) ||
+	    skip_prefix(var, "color.diff.", &name)) {
+		int slot = parse_diff_color_slot(name);
 		if (slot < 0)
 			return 0;
 		if (!value)
@@ -2341,6 +2344,7 @@ static void builtin_diff(const char *name_a,
 	} else {
 		/* Crazy xdl interfaces.. */
 		const char *diffopts = getenv("GIT_DIFF_OPTS");
+		const char *v;
 		xpparam_t xpp;
 		xdemitconf_t xecfg;
 		struct emit_callback ecbdata;
@@ -2379,10 +2383,10 @@ static void builtin_diff(const char *name_a,
 			xdiff_set_find_func(&xecfg, pe->pattern, pe->cflags);
 		if (!diffopts)
 			;
-		else if (starts_with(diffopts, "--unified="))
-			xecfg.ctxlen = strtoul(diffopts + 10, NULL, 10);
-		else if (starts_with(diffopts, "-u"))
-			xecfg.ctxlen = strtoul(diffopts + 2, NULL, 10);
+		else if (skip_prefix(diffopts, "--unified=", &v))
+			xecfg.ctxlen = strtoul(v, NULL, 10);
+		else if (skip_prefix(diffopts, "-u", &v))
+			xecfg.ctxlen = strtoul(v, NULL, 10);
 		if (o->word_diff)
 			init_diff_words_data(&ecbdata, o, one, two);
 		xdi_diff_outf(&mf1, &mf2, fn_out_consume, &ecbdata,
@@ -3391,12 +3395,10 @@ int parse_long_opt(const char *opt, const char **argv,
 		   const char **optarg)
 {
 	const char *arg = argv[0];
-	if (arg[0] != '-' || arg[1] != '-')
+	if (!skip_prefix(arg, "--", &arg))
 		return 0;
-	arg += strlen("--");
-	if (!starts_with(arg, opt))
+	if (!skip_prefix(arg, opt, &arg))
 		return 0;
-	arg += strlen(opt);
 	if (*arg == '=') { /* stuck form: --option=value */
 		*optarg = arg + 1;
 		return 1;
@@ -3420,13 +3422,13 @@ static int stat_opt(struct diff_options *options, const char **av)
 	int count = options->stat_count;
 	int argcount = 1;
 
-	arg += strlen("--stat");
+	if (!skip_prefix(arg, "--stat", &arg))
+		die("BUG: stat option does not begin with --stat: %s", arg);
 	end = (char *)arg;
 
 	switch (*arg) {
 	case '-':
-		if (starts_with(arg, "-width")) {
-			arg += strlen("-width");
+		if (skip_prefix(arg, "-width", &arg)) {
 			if (*arg == '=')
 				width = strtoul(arg + 1, &end, 10);
 			else if (!*arg && !av[1])
@@ -3435,8 +3437,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 				width = strtoul(av[1], &end, 10);
 				argcount = 2;
 			}
-		} else if (starts_with(arg, "-name-width")) {
-			arg += strlen("-name-width");
+		} else if (skip_prefix(arg, "-name-width", &arg)) {
 			if (*arg == '=')
 				name_width = strtoul(arg + 1, &end, 10);
 			else if (!*arg && !av[1])
@@ -3445,8 +3446,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 				name_width = strtoul(av[1], &end, 10);
 				argcount = 2;
 			}
-		} else if (starts_with(arg, "-graph-width")) {
-			arg += strlen("-graph-width");
+		} else if (skip_prefix(arg, "-graph-width", &arg)) {
 			if (*arg == '=')
 				graph_width = strtoul(arg + 1, &end, 10);
 			else if (!*arg && !av[1])
@@ -3455,8 +3455,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 				graph_width = strtoul(av[1], &end, 10);
 				argcount = 2;
 			}
-		} else if (starts_with(arg, "-count")) {
-			arg += strlen("-count");
+		} else if (skip_prefix(arg, "-count", &arg)) {
 			if (*arg == '=')
 				count = strtoul(arg + 1, &end, 10);
 			else if (!*arg && !av[1])
@@ -3609,17 +3608,17 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		options->output_format |= DIFF_FORMAT_SHORTSTAT;
 	else if (!strcmp(arg, "-X") || !strcmp(arg, "--dirstat"))
 		return parse_dirstat_opt(options, "");
-	else if (starts_with(arg, "-X"))
-		return parse_dirstat_opt(options, arg + 2);
-	else if (starts_with(arg, "--dirstat="))
-		return parse_dirstat_opt(options, arg + 10);
+	else if (skip_prefix(arg, "-X", &arg))
+		return parse_dirstat_opt(options, arg);
+	else if (skip_prefix(arg, "--dirstat=", &arg))
+		return parse_dirstat_opt(options, arg);
 	else if (!strcmp(arg, "--cumulative"))
 		return parse_dirstat_opt(options, "cumulative");
 	else if (!strcmp(arg, "--dirstat-by-file"))
 		return parse_dirstat_opt(options, "files");
-	else if (starts_with(arg, "--dirstat-by-file=")) {
+	else if (skip_prefix(arg, "--dirstat-by-file=", &arg)) {
 		parse_dirstat_opt(options, "files");
-		return parse_dirstat_opt(options, arg + 18);
+		return parse_dirstat_opt(options, arg);
 	}
 	else if (!strcmp(arg, "--check"))
 		options->output_format |= DIFF_FORMAT_CHECKDIFF;
@@ -3669,9 +3668,9 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		DIFF_OPT_CLR(options, RENAME_EMPTY);
 	else if (!strcmp(arg, "--relative"))
 		DIFF_OPT_SET(options, RELATIVE_NAME);
-	else if (starts_with(arg, "--relative=")) {
+	else if (skip_prefix(arg, "--relative=", &arg)) {
 		DIFF_OPT_SET(options, RELATIVE_NAME);
-		options->prefix = arg + 11;
+		options->prefix = arg;
 	}
 
 	/* xdiff options */
@@ -3722,8 +3721,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		DIFF_OPT_CLR(options, FOLLOW_RENAMES);
 	else if (!strcmp(arg, "--color"))
 		options->use_color = 1;
-	else if (starts_with(arg, "--color=")) {
-		int value = git_config_colorbool(NULL, arg+8);
+	else if (skip_prefix(arg, "--color=", &arg)) {
+		int value = git_config_colorbool(NULL, arg);
 		if (value < 0)
 			return error("option `color' expects \"always\", \"auto\", or \"never\"");
 		options->use_color = value;
@@ -3734,29 +3733,28 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		options->use_color = 1;
 		options->word_diff = DIFF_WORDS_COLOR;
 	}
-	else if (starts_with(arg, "--color-words=")) {
+	else if (skip_prefix(arg, "--color-words=", &arg)) {
 		options->use_color = 1;
 		options->word_diff = DIFF_WORDS_COLOR;
-		options->word_regex = arg + 14;
+		options->word_regex = arg;
 	}
 	else if (!strcmp(arg, "--word-diff")) {
 		if (options->word_diff == DIFF_WORDS_NONE)
 			options->word_diff = DIFF_WORDS_PLAIN;
 	}
-	else if (starts_with(arg, "--word-diff=")) {
-		const char *type = arg + 12;
-		if (!strcmp(type, "plain"))
+	else if (skip_prefix(arg, "--word-diff=", &arg)) {
+		if (!strcmp(arg, "plain"))
 			options->word_diff = DIFF_WORDS_PLAIN;
-		else if (!strcmp(type, "color")) {
+		else if (!strcmp(arg, "color")) {
 			options->use_color = 1;
 			options->word_diff = DIFF_WORDS_COLOR;
 		}
-		else if (!strcmp(type, "porcelain"))
+		else if (!strcmp(arg, "porcelain"))
 			options->word_diff = DIFF_WORDS_PORCELAIN;
-		else if (!strcmp(type, "none"))
+		else if (!strcmp(arg, "none"))
 			options->word_diff = DIFF_WORDS_NONE;
 		else
-			die("bad --word-diff argument: %s", type);
+			die("bad --word-diff argument: %s", arg);
 	}
 	else if ((argcount = parse_long_opt("word-diff-regex", av, &optarg))) {
 		if (options->word_diff == DIFF_WORDS_NONE)
@@ -3779,13 +3777,13 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (!strcmp(arg, "--ignore-submodules")) {
 		DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);
 		handle_ignore_submodules_arg(options, "all");
-	} else if (starts_with(arg, "--ignore-submodules=")) {
+	} else if (skip_prefix(arg, "--ignore-submodules=", &arg)) {
 		DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);
-		handle_ignore_submodules_arg(options, arg + 20);
+		handle_ignore_submodules_arg(options, arg);
 	} else if (!strcmp(arg, "--submodule"))
 		DIFF_OPT_SET(options, SUBMODULE_LOG);
-	else if (starts_with(arg, "--submodule="))
-		return parse_submodule_opt(options, arg + 12);
+	else if (skip_prefix(arg, "--submodule=", &arg))
+		return parse_submodule_opt(options, arg);
 
 	/* misc options */
 	else if (!strcmp(arg, "-z"))
@@ -3820,8 +3818,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	}
 	else if (!strcmp(arg, "--abbrev"))
 		options->abbrev = DEFAULT_ABBREV;
-	else if (starts_with(arg, "--abbrev=")) {
-		options->abbrev = strtoul(arg + 9, NULL, 10);
+	else if (skip_prefix(arg, "--abbrev=", &arg)) {
+		options->abbrev = strtoul(arg, NULL, 10);
 		if (options->abbrev < MINIMUM_ABBREV)
 			options->abbrev = MINIMUM_ABBREV;
 		else if (40 < options->abbrev)
@@ -3902,16 +3900,13 @@ static int diff_scoreopt_parse(const char *opt)
 	cmd = *opt++;
 	if (cmd == '-') {
 		/* convert the long-form arguments into short-form versions */
-		if (starts_with(opt, "break-rewrites")) {
-			opt += strlen("break-rewrites");
+		if (skip_prefix(opt, "break-rewrites", &opt)) {
 			if (*opt == 0 || *opt++ == '=')
 				cmd = 'B';
-		} else if (starts_with(opt, "find-copies")) {
-			opt += strlen("find-copies");
+		} else if (skip_prefix(opt, "find-copies", &opt)) {
 			if (*opt == 0 || *opt++ == '=')
 				cmd = 'C';
-		} else if (starts_with(opt, "find-renames")) {
-			opt += strlen("find-renames");
+		} else if (skip_prefix(opt, "find-renames", &opt)) {
 			if (*opt == 0 || *opt++ == '=')
 				cmd = 'M';
 		}
diff --git a/fast-import.c b/fast-import.c
index 6707a66471..fa635f75c3 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -371,8 +371,8 @@ static volatile sig_atomic_t checkpoint_requested;
 static int cat_blob_fd = STDOUT_FILENO;
 
 static void parse_argv(void);
-static void parse_cat_blob(void);
-static void parse_ls(struct branch *b);
+static void parse_cat_blob(const char *p);
+static void parse_ls(const char *p, struct branch *b);
 
 static void write_branch_report(FILE *rpt, struct branch *b)
 {
@@ -1861,6 +1861,8 @@ static int read_next_command(void)
 	}
 
 	for (;;) {
+		const char *p;
+
 		if (unread_command_buf) {
 			unread_command_buf = 0;
 		} else {
@@ -1893,8 +1895,8 @@ static int read_next_command(void)
 			rc->prev->next = rc;
 			cmd_tail = rc;
 		}
-		if (starts_with(command_buf.buf, "cat-blob ")) {
-			parse_cat_blob();
+		if (skip_prefix(command_buf.buf, "cat-blob ", &p)) {
+			parse_cat_blob(p);
 			continue;
 		}
 		if (command_buf.buf[0] == '#')
@@ -1912,8 +1914,9 @@ static void skip_optional_lf(void)
 
 static void parse_mark(void)
 {
-	if (starts_with(command_buf.buf, "mark :")) {
-		next_mark = strtoumax(command_buf.buf + 6, NULL, 10);
+	const char *v;
+	if (skip_prefix(command_buf.buf, "mark :", &v)) {
+		next_mark = strtoumax(v, NULL, 10);
 		read_next_command();
 	}
 	else
@@ -1922,14 +1925,15 @@ static void parse_mark(void)
 
 static int parse_data(struct strbuf *sb, uintmax_t limit, uintmax_t *len_res)
 {
+	const char *data;
 	strbuf_reset(sb);
 
-	if (!starts_with(command_buf.buf, "data "))
+	if (!skip_prefix(command_buf.buf, "data ", &data))
 		die("Expected 'data n' command, found: %s", command_buf.buf);
 
-	if (starts_with(command_buf.buf + 5, "<<")) {
-		char *term = xstrdup(command_buf.buf + 5 + 2);
-		size_t term_len = command_buf.len - 5 - 2;
+	if (skip_prefix(data, "<<", &data)) {
+		char *term = xstrdup(data);
+		size_t term_len = command_buf.len - (data - command_buf.buf);
 
 		strbuf_detach(&command_buf, NULL);
 		for (;;) {
@@ -1944,7 +1948,7 @@ static int parse_data(struct strbuf *sb, uintmax_t limit, uintmax_t *len_res)
 		free(term);
 	}
 	else {
-		uintmax_t len = strtoumax(command_buf.buf + 5, NULL, 10);
+		uintmax_t len = strtoumax(data, NULL, 10);
 		size_t n = 0, length = (size_t)len;
 
 		if (limit && limit < len) {
@@ -2265,15 +2269,14 @@ static uintmax_t parse_mark_ref_space(const char **p)
 	char *end;
 
 	mark = parse_mark_ref(*p, &end);
-	if (*end != ' ')
+	if (*end++ != ' ')
 		die("Missing space after mark: %s", command_buf.buf);
 	*p = end;
 	return mark;
 }
 
-static void file_change_m(struct branch *b)
+static void file_change_m(const char *p, struct branch *b)
 {
-	const char *p = command_buf.buf + 2;
 	static struct strbuf uq = STRBUF_INIT;
 	const char *endp;
 	struct object_entry *oe;
@@ -2301,20 +2304,17 @@ static void file_change_m(struct branch *b)
 	if (*p == ':') {
 		oe = find_mark(parse_mark_ref_space(&p));
 		hashcpy(sha1, oe->idx.sha1);
-	} else if (starts_with(p, "inline ")) {
+	} else if (skip_prefix(p, "inline ", &p)) {
 		inline_data = 1;
 		oe = NULL; /* not used with inline_data, but makes gcc happy */
-		p += strlen("inline");  /* advance to space */
 	} else {
 		if (get_sha1_hex(p, sha1))
 			die("Invalid dataref: %s", command_buf.buf);
 		oe = find_object(sha1);
 		p += 40;
-		if (*p != ' ')
+		if (*p++ != ' ')
 			die("Missing space after SHA1: %s", command_buf.buf);
 	}
-	assert(*p == ' ');
-	p++;  /* skip space */
 
 	strbuf_reset(&uq);
 	if (!unquote_c_style(&uq, p, &endp)) {
@@ -2374,9 +2374,8 @@ static void file_change_m(struct branch *b)
 	tree_content_set(&b->branch_tree, p, sha1, mode, NULL);
 }
 
-static void file_change_d(struct branch *b)
+static void file_change_d(const char *p, struct branch *b)
 {
-	const char *p = command_buf.buf + 2;
 	static struct strbuf uq = STRBUF_INIT;
 	const char *endp;
 
@@ -2389,15 +2388,14 @@ static void file_change_d(struct branch *b)
 	tree_content_remove(&b->branch_tree, p, NULL, 1);
 }
 
-static void file_change_cr(struct branch *b, int rename)
+static void file_change_cr(const char *s, struct branch *b, int rename)
 {
-	const char *s, *d;
+	const char *d;
 	static struct strbuf s_uq = STRBUF_INIT;
 	static struct strbuf d_uq = STRBUF_INIT;
 	const char *endp;
 	struct tree_entry leaf;
 
-	s = command_buf.buf + 2;
 	strbuf_reset(&s_uq);
 	if (!unquote_c_style(&s_uq, s, &endp)) {
 		if (*endp != ' ')
@@ -2442,9 +2440,8 @@ static void file_change_cr(struct branch *b, int rename)
 		leaf.tree);
 }
 
-static void note_change_n(struct branch *b, unsigned char *old_fanout)
+static void note_change_n(const char *p, struct branch *b, unsigned char *old_fanout)
 {
-	const char *p = command_buf.buf + 2;
 	static struct strbuf uq = STRBUF_INIT;
 	struct object_entry *oe;
 	struct branch *s;
@@ -2474,20 +2471,17 @@ static void note_change_n(struct branch *b, unsigned char *old_fanout)
 	if (*p == ':') {
 		oe = find_mark(parse_mark_ref_space(&p));
 		hashcpy(sha1, oe->idx.sha1);
-	} else if (starts_with(p, "inline ")) {
+	} else if (skip_prefix(p, "inline ", &p)) {
 		inline_data = 1;
 		oe = NULL; /* not used with inline_data, but makes gcc happy */
-		p += strlen("inline");  /* advance to space */
 	} else {
 		if (get_sha1_hex(p, sha1))
 			die("Invalid dataref: %s", command_buf.buf);
 		oe = find_object(sha1);
 		p += 40;
-		if (*p != ' ')
+		if (*p++ != ' ')
 			die("Missing space after SHA1: %s", command_buf.buf);
 	}
-	assert(*p == ' ');
-	p++;  /* skip space */
 
 	/* <commit-ish> */
 	s = lookup_branch(p);
@@ -2585,7 +2579,7 @@ static int parse_from(struct branch *b)
 	const char *from;
 	struct branch *s;
 
-	if (!starts_with(command_buf.buf, "from "))
+	if (!skip_prefix(command_buf.buf, "from ", &from))
 		return 0;
 
 	if (b->branch_tree.tree) {
@@ -2593,7 +2587,6 @@ static int parse_from(struct branch *b)
 		b->branch_tree.tree = NULL;
 	}
 
-	from = strchr(command_buf.buf, ' ') + 1;
 	s = lookup_branch(from);
 	if (b == s)
 		die("Can't create a branch from itself: %s", b->name);
@@ -2634,8 +2627,7 @@ static struct hash_list *parse_merge(unsigned int *count)
 	struct branch *s;
 
 	*count = 0;
-	while (starts_with(command_buf.buf, "merge ")) {
-		from = strchr(command_buf.buf, ' ') + 1;
+	while (skip_prefix(command_buf.buf, "merge ", &from)) {
 		n = xmalloc(sizeof(*n));
 		s = lookup_branch(from);
 		if (s)
@@ -2666,31 +2658,29 @@ static struct hash_list *parse_merge(unsigned int *count)
 	return list;
 }
 
-static void parse_new_commit(void)
+static void parse_new_commit(const char *arg)
 {
 	static struct strbuf msg = STRBUF_INIT;
 	struct branch *b;
-	char *sp;
 	char *author = NULL;
 	char *committer = NULL;
 	struct hash_list *merge_list = NULL;
 	unsigned int merge_count;
 	unsigned char prev_fanout, new_fanout;
+	const char *v;
 
-	/* Obtain the branch name from the rest of our command */
-	sp = strchr(command_buf.buf, ' ') + 1;
-	b = lookup_branch(sp);
+	b = lookup_branch(arg);
 	if (!b)
-		b = new_branch(sp);
+		b = new_branch(arg);
 
 	read_next_command();
 	parse_mark();
-	if (starts_with(command_buf.buf, "author ")) {
-		author = parse_ident(command_buf.buf + 7);
+	if (skip_prefix(command_buf.buf, "author ", &v)) {
+		author = parse_ident(v);
 		read_next_command();
 	}
-	if (starts_with(command_buf.buf, "committer ")) {
-		committer = parse_ident(command_buf.buf + 10);
+	if (skip_prefix(command_buf.buf, "committer ", &v)) {
+		committer = parse_ident(v);
 		read_next_command();
 	}
 	if (!committer)
@@ -2710,20 +2700,20 @@ static void parse_new_commit(void)
 
 	/* file_change* */
 	while (command_buf.len > 0) {
-		if (starts_with(command_buf.buf, "M "))
-			file_change_m(b);
-		else if (starts_with(command_buf.buf, "D "))
-			file_change_d(b);
-		else if (starts_with(command_buf.buf, "R "))
-			file_change_cr(b, 1);
-		else if (starts_with(command_buf.buf, "C "))
-			file_change_cr(b, 0);
-		else if (starts_with(command_buf.buf, "N "))
-			note_change_n(b, &prev_fanout);
+		if (skip_prefix(command_buf.buf, "M ", &v))
+			file_change_m(v, b);
+		else if (skip_prefix(command_buf.buf, "D ", &v))
+			file_change_d(v, b);
+		else if (skip_prefix(command_buf.buf, "R ", &v))
+			file_change_cr(v, b, 1);
+		else if (skip_prefix(command_buf.buf, "C ", &v))
+			file_change_cr(v, b, 0);
+		else if (skip_prefix(command_buf.buf, "N ", &v))
+			note_change_n(v, b, &prev_fanout);
 		else if (!strcmp("deleteall", command_buf.buf))
 			file_change_deleteall(b);
-		else if (starts_with(command_buf.buf, "ls "))
-			parse_ls(b);
+		else if (skip_prefix(command_buf.buf, "ls ", &v))
+			parse_ls(v, b);
 		else {
 			unread_command_buf = 1;
 			break;
@@ -2766,10 +2756,9 @@ static void parse_new_commit(void)
 	b->last_commit = object_count_by_type[OBJ_COMMIT];
 }
 
-static void parse_new_tag(void)
+static void parse_new_tag(const char *arg)
 {
 	static struct strbuf msg = STRBUF_INIT;
-	char *sp;
 	const char *from;
 	char *tagger;
 	struct branch *s;
@@ -2777,12 +2766,11 @@ static void parse_new_tag(void)
 	uintmax_t from_mark = 0;
 	unsigned char sha1[20];
 	enum object_type type;
+	const char *v;
 
-	/* Obtain the new tag name from the rest of our command */
-	sp = strchr(command_buf.buf, ' ') + 1;
 	t = pool_alloc(sizeof(struct tag));
 	memset(t, 0, sizeof(struct tag));
-	t->name = pool_strdup(sp);
+	t->name = pool_strdup(arg);
 	if (last_tag)
 		last_tag->next_tag = t;
 	else
@@ -2791,9 +2779,8 @@ static void parse_new_tag(void)
 	read_next_command();
 
 	/* from ... */
-	if (!starts_with(command_buf.buf, "from "))
+	if (!skip_prefix(command_buf.buf, "from ", &from))
 		die("Expected from command, got %s", command_buf.buf);
-	from = strchr(command_buf.buf, ' ') + 1;
 	s = lookup_branch(from);
 	if (s) {
 		if (is_null_sha1(s->sha1))
@@ -2819,8 +2806,8 @@ static void parse_new_tag(void)
 	read_next_command();
 
 	/* tagger ... */
-	if (starts_with(command_buf.buf, "tagger ")) {
-		tagger = parse_ident(command_buf.buf + 7);
+	if (skip_prefix(command_buf.buf, "tagger ", &v)) {
+		tagger = parse_ident(v);
 		read_next_command();
 	} else
 		tagger = NULL;
@@ -2849,14 +2836,11 @@ static void parse_new_tag(void)
 		t->pack_id = pack_id;
 }
 
-static void parse_reset_branch(void)
+static void parse_reset_branch(const char *arg)
 {
 	struct branch *b;
-	char *sp;
 
-	/* Obtain the branch name from the rest of our command */
-	sp = strchr(command_buf.buf, ' ') + 1;
-	b = lookup_branch(sp);
+	b = lookup_branch(arg);
 	if (b) {
 		hashclr(b->sha1);
 		hashclr(b->branch_tree.versions[0].sha1);
@@ -2867,7 +2851,7 @@ static void parse_reset_branch(void)
 		}
 	}
 	else
-		b = new_branch(sp);
+		b = new_branch(arg);
 	read_next_command();
 	parse_from(b);
 	if (command_buf.len > 0)
@@ -2925,14 +2909,12 @@ static void cat_blob(struct object_entry *oe, unsigned char sha1[20])
 		free(buf);
 }
 
-static void parse_cat_blob(void)
+static void parse_cat_blob(const char *p)
 {
-	const char *p;
 	struct object_entry *oe = oe;
 	unsigned char sha1[20];
 
 	/* cat-blob SP <object> LF */
-	p = command_buf.buf + strlen("cat-blob ");
 	if (*p == ':') {
 		oe = find_mark(parse_mark_ref_eol(p));
 		if (!oe)
@@ -3015,6 +2997,8 @@ static struct object_entry *parse_treeish_dataref(const char **p)
 			die("Invalid dataref: %s", command_buf.buf);
 		e = find_object(sha1);
 		*p += 40;
+		if (*(*p)++ != ' ')
+			die("Missing space after tree-ish: %s", command_buf.buf);
 	}
 
 	while (!e || e->type != OBJ_TREE)
@@ -3049,14 +3033,12 @@ static void print_ls(int mode, const unsigned char *sha1, const char *path)
 	cat_blob_write(line.buf, line.len);
 }
 
-static void parse_ls(struct branch *b)
+static void parse_ls(const char *p, struct branch *b)
 {
-	const char *p;
 	struct tree_entry *root = NULL;
 	struct tree_entry leaf = {NULL};
 
 	/* ls SP (<tree-ish> SP)? <path> */
-	p = command_buf.buf + strlen("ls ");
 	if (*p == '"') {
 		if (!b)
 			die("Not in a commit: %s", command_buf.buf);
@@ -3068,8 +3050,6 @@ static void parse_ls(struct branch *b)
 		if (!is_null_sha1(root->versions[1].sha1))
 			root->versions[1].mode = S_IFDIR;
 		load_tree(root);
-		if (*p++ != ' ')
-			die("Missing space after tree-ish: %s", command_buf.buf);
 	}
 	if (*p == '"') {
 		static struct strbuf uq = STRBUF_INIT;
@@ -3207,9 +3187,9 @@ static void option_export_pack_edges(const char *edges)
 
 static int parse_one_option(const char *option)
 {
-	if (starts_with(option, "max-pack-size=")) {
+	if (skip_prefix(option, "max-pack-size=", &option)) {
 		unsigned long v;
-		if (!git_parse_ulong(option + 14, &v))
+		if (!git_parse_ulong(option, &v))
 			return 0;
 		if (v < 8192) {
 			warning("max-pack-size is now in bytes, assuming --max-pack-size=%lum", v);
@@ -3219,17 +3199,17 @@ static int parse_one_option(const char *option)
 			v = 1024 * 1024;
 		}
 		max_packsize = v;
-	} else if (starts_with(option, "big-file-threshold=")) {
+	} else if (skip_prefix(option, "big-file-threshold=", &option)) {
 		unsigned long v;
-		if (!git_parse_ulong(option + 19, &v))
+		if (!git_parse_ulong(option, &v))
 			return 0;
 		big_file_threshold = v;
-	} else if (starts_with(option, "depth=")) {
-		option_depth(option + 6);
-	} else if (starts_with(option, "active-branches=")) {
-		option_active_branches(option + 16);
-	} else if (starts_with(option, "export-pack-edges=")) {
-		option_export_pack_edges(option + 18);
+	} else if (skip_prefix(option, "depth=", &option)) {
+		option_depth(option);
+	} else if (skip_prefix(option, "active-branches=", &option)) {
+		option_active_branches(option);
+	} else if (skip_prefix(option, "export-pack-edges=", &option)) {
+		option_export_pack_edges(option);
 	} else if (starts_with(option, "quiet")) {
 		show_stats = 0;
 	} else if (starts_with(option, "stats")) {
@@ -3243,15 +3223,16 @@ static int parse_one_option(const char *option)
 
 static int parse_one_feature(const char *feature, int from_stream)
 {
-	if (starts_with(feature, "date-format=")) {
-		option_date_format(feature + 12);
-	} else if (starts_with(feature, "import-marks=")) {
-		option_import_marks(feature + 13, from_stream, 0);
-	} else if (starts_with(feature, "import-marks-if-exists=")) {
-		option_import_marks(feature + strlen("import-marks-if-exists="),
-					from_stream, 1);
-	} else if (starts_with(feature, "export-marks=")) {
-		option_export_marks(feature + 13);
+	const char *arg;
+
+	if (skip_prefix(feature, "date-format=", &arg)) {
+		option_date_format(arg);
+	} else if (skip_prefix(feature, "import-marks=", &arg)) {
+		option_import_marks(arg, from_stream, 0);
+	} else if (skip_prefix(feature, "import-marks-if-exists=", &arg)) {
+		option_import_marks(arg, from_stream, 1);
+	} else if (skip_prefix(feature, "export-marks=", &arg)) {
+		option_export_marks(arg);
 	} else if (!strcmp(feature, "cat-blob")) {
 		; /* Don't die - this feature is supported */
 	} else if (!strcmp(feature, "relative-marks")) {
@@ -3271,10 +3252,8 @@ static int parse_one_feature(const char *feature, int from_stream)
 	return 1;
 }
 
-static void parse_feature(void)
+static void parse_feature(const char *feature)
 {
-	char *feature = command_buf.buf + 8;
-
 	if (seen_data_command)
 		die("Got feature command '%s' after data command", feature);
 
@@ -3284,10 +3263,8 @@ static void parse_feature(void)
 	die("This version of fast-import does not support feature %s.", feature);
 }
 
-static void parse_option(void)
+static void parse_option(const char *option)
 {
-	char *option = command_buf.buf + 11;
-
 	if (seen_data_command)
 		die("Got option command '%s' after data command", option);
 
@@ -3342,18 +3319,21 @@ static void parse_argv(void)
 		if (*a != '-' || !strcmp(a, "--"))
 			break;
 
-		if (parse_one_option(a + 2))
+		if (!skip_prefix(a, "--", &a))
+			die("unknown option %s", a);
+
+		if (parse_one_option(a))
 			continue;
 
-		if (parse_one_feature(a + 2, 0))
+		if (parse_one_feature(a, 0))
 			continue;
 
-		if (starts_with(a + 2, "cat-blob-fd=")) {
-			option_cat_blob_fd(a + 2 + strlen("cat-blob-fd="));
+		if (skip_prefix(a, "cat-blob-fd=", &a)) {
+			option_cat_blob_fd(a);
 			continue;
 		}
 
-		die("unknown option %s", a);
+		die("unknown option --%s", a);
 	}
 	if (i != global_argc)
 		usage(fast_import_usage);
@@ -3400,26 +3380,27 @@ int main(int argc, char **argv)
 	set_die_routine(die_nicely);
 	set_checkpoint_signal();
 	while (read_next_command() != EOF) {
+		const char *v;
 		if (!strcmp("blob", command_buf.buf))
 			parse_new_blob();
-		else if (starts_with(command_buf.buf, "ls "))
-			parse_ls(NULL);
-		else if (starts_with(command_buf.buf, "commit "))
-			parse_new_commit();
-		else if (starts_with(command_buf.buf, "tag "))
-			parse_new_tag();
-		else if (starts_with(command_buf.buf, "reset "))
-			parse_reset_branch();
+		else if (skip_prefix(command_buf.buf, "ls ", &v))
+			parse_ls(v, NULL);
+		else if (skip_prefix(command_buf.buf, "commit ", &v))
+			parse_new_commit(v);
+		else if (skip_prefix(command_buf.buf, "tag ", &v))
+			parse_new_tag(v);
+		else if (skip_prefix(command_buf.buf, "reset ", &v))
+			parse_reset_branch(v);
 		else if (!strcmp("checkpoint", command_buf.buf))
 			parse_checkpoint();
 		else if (!strcmp("done", command_buf.buf))
 			break;
 		else if (starts_with(command_buf.buf, "progress "))
 			parse_progress();
-		else if (starts_with(command_buf.buf, "feature "))
-			parse_feature();
-		else if (starts_with(command_buf.buf, "option git "))
-			parse_option();
+		else if (skip_prefix(command_buf.buf, "feature ", &v))
+			parse_feature(v);
+		else if (skip_prefix(command_buf.buf, "option git ", &v))
+			parse_option(v);
 		else if (starts_with(command_buf.buf, "option "))
 			/* ignore non-git options*/;
 		else
diff --git a/fetch-pack.c b/fetch-pack.c
index b12bd4c59a..b8a58fa7a5 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -189,20 +189,23 @@ static enum ack_type get_ack(int fd, unsigned char *result_sha1)
 {
 	int len;
 	char *line = packet_read_line(fd, &len);
+	const char *arg;
 
 	if (!len)
 		die("git fetch-pack: expected ACK/NAK, got EOF");
 	if (!strcmp(line, "NAK"))
 		return NAK;
-	if (starts_with(line, "ACK ")) {
-		if (!get_sha1_hex(line+4, result_sha1)) {
-			if (len < 45)
+	if (skip_prefix(line, "ACK ", &arg)) {
+		if (!get_sha1_hex(arg, result_sha1)) {
+			arg += 40;
+			len -= arg - line;
+			if (len < 1)
 				return ACK;
-			if (strstr(line+45, "continue"))
+			if (strstr(arg, "continue"))
 				return ACK_continue;
-			if (strstr(line+45, "common"))
+			if (strstr(arg, "common"))
 				return ACK_common;
-			if (strstr(line+45, "ready"))
+			if (strstr(arg, "ready"))
 				return ACK_ready;
 			return ACK;
 		}
@@ -319,18 +322,19 @@ static int find_common(struct fetch_pack_args *args,
 
 	if (args->depth > 0) {
 		char *line;
+		const char *arg;
 		unsigned char sha1[20];
 
 		send_request(args, fd[1], &req_buf);
 		while ((line = packet_read_line(fd[0], NULL))) {
-			if (starts_with(line, "shallow ")) {
-				if (get_sha1_hex(line + 8, sha1))
+			if (skip_prefix(line, "shallow ", &arg)) {
+				if (get_sha1_hex(arg, sha1))
 					die("invalid shallow line: %s", line);
 				register_shallow(sha1);
 				continue;
 			}
-			if (starts_with(line, "unshallow ")) {
-				if (get_sha1_hex(line + 10, sha1))
+			if (skip_prefix(line, "unshallow ", &arg)) {
+				if (get_sha1_hex(arg, sha1))
 					die("invalid unshallow line: %s", line);
 				if (!lookup_object(sha1))
 					die("object not found: %s", line);
diff --git a/fsck.c b/fsck.c
index a7233c8d0b..a4e8593e78 100644
--- a/fsck.c
+++ b/fsck.c
@@ -279,20 +279,17 @@ static int fsck_ident(const char **ident, struct object *obj, fsck_error error_f
 static int fsck_commit_buffer(struct commit *commit, const char *buffer,
 			      fsck_error error_func)
 {
-	const char *tmp;
 	unsigned char tree_sha1[20], sha1[20];
 	struct commit_graft *graft;
 	int parents = 0;
 	int err;
 
-	buffer = skip_prefix(buffer, "tree ");
-	if (!buffer)
+	if (!skip_prefix(buffer, "tree ", &buffer))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line");
 	if (get_sha1_hex(buffer, tree_sha1) || buffer[40] != '\n')
 		return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1");
 	buffer += 41;
-	while ((tmp = skip_prefix(buffer, "parent "))) {
-		buffer = tmp;
+	while (skip_prefix(buffer, "parent ", &buffer)) {
 		if (get_sha1_hex(buffer, sha1) || buffer[40] != '\n')
 			return error_func(&commit->object, FSCK_ERROR, "invalid 'parent' line format - bad sha1");
 		buffer += 41;
@@ -319,14 +316,12 @@ static int fsck_commit_buffer(struct commit *commit, const char *buffer,
 		if (p || parents)
 			return error_func(&commit->object, FSCK_ERROR, "parent objects missing");
 	}
-	buffer = skip_prefix(buffer, "author ");
-	if (!buffer)
+	if (!skip_prefix(buffer, "author ", &buffer))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'author' line");
 	err = fsck_ident(&buffer, &commit->object, error_func);
 	if (err)
 		return err;
-	buffer = skip_prefix(buffer, "committer ");
-	if (!buffer)
+	if (!skip_prefix(buffer, "committer ", &buffer))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'committer' line");
 	err = fsck_ident(&buffer, &commit->object, error_func);
 	if (err)
diff --git a/git-compat-util.h b/git-compat-util.h
index 96f55547a3..9de3180710 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -349,13 +349,32 @@ extern void set_die_is_recursing_routine(int (*routine)(void));
 extern int starts_with(const char *str, const char *prefix);
 extern int ends_with(const char *str, const char *suffix);
 
-static inline const char *skip_prefix(const char *str, const char *prefix)
+/*
+ * If the string "str" begins with the string found in "prefix", return 1.
+ * The "out" parameter is set to "str + strlen(prefix)" (i.e., to the point in
+ * the string right after the prefix).
+ *
+ * Otherwise, return 0 and leave "out" untouched.
+ *
+ * Examples:
+ *
+ *   [extract branch name, fail if not a branch]
+ *   if (!skip_prefix(ref, "refs/heads/", &branch)
+ *	return -1;
+ *
+ *   [skip prefix if present, otherwise use whole string]
+ *   skip_prefix(name, "refs/heads/", &name);
+ */
+static inline int skip_prefix(const char *str, const char *prefix,
+			      const char **out)
 {
 	do {
-		if (!*prefix)
-			return str;
+		if (!*prefix) {
+			*out = str;
+			return 1;
+		}
 	} while (*str++ == *prefix++);
-	return NULL;
+	return 0;
 }
 
 #if defined(NO_MMAP) || defined(USE_WIN32_MMAP)
diff --git a/git.c b/git.c
index d6b4a5543f..dd54f5734a 100644
--- a/git.c
+++ b/git.c
@@ -91,8 +91,7 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 		/*
 		 * Check remaining flags.
 		 */
-		if (starts_with(cmd, "--exec-path")) {
-			cmd += 11;
+		if (skip_prefix(cmd, "--exec-path", &cmd)) {
 			if (*cmd == '=')
 				git_set_argv_exec_path(cmd + 1);
 			else {
@@ -129,8 +128,8 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 				*envchanged = 1;
 			(*argv)++;
 			(*argc)--;
-		} else if (starts_with(cmd, "--git-dir=")) {
-			setenv(GIT_DIR_ENVIRONMENT, cmd + 10, 1);
+		} else if (skip_prefix(cmd, "--git-dir=", &cmd)) {
+			setenv(GIT_DIR_ENVIRONMENT, cmd, 1);
 			if (envchanged)
 				*envchanged = 1;
 		} else if (!strcmp(cmd, "--namespace")) {
@@ -143,8 +142,8 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 				*envchanged = 1;
 			(*argv)++;
 			(*argc)--;
-		} else if (starts_with(cmd, "--namespace=")) {
-			setenv(GIT_NAMESPACE_ENVIRONMENT, cmd + 12, 1);
+		} else if (skip_prefix(cmd, "--namespace=", &cmd)) {
+			setenv(GIT_NAMESPACE_ENVIRONMENT, cmd, 1);
 			if (envchanged)
 				*envchanged = 1;
 		} else if (!strcmp(cmd, "--work-tree")) {
@@ -157,8 +156,8 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 				*envchanged = 1;
 			(*argv)++;
 			(*argc)--;
-		} else if (starts_with(cmd, "--work-tree=")) {
-			setenv(GIT_WORK_TREE_ENVIRONMENT, cmd + 12, 1);
+		} else if (skip_prefix(cmd, "--work-tree=", &cmd)) {
+			setenv(GIT_WORK_TREE_ENVIRONMENT, cmd, 1);
 			if (envchanged)
 				*envchanged = 1;
 		} else if (!strcmp(cmd, "--bare")) {
@@ -623,8 +622,7 @@ int main(int argc, char **av)
 	 * So we just directly call the builtin handler, and die if
 	 * that one cannot handle it.
 	 */
-	if (starts_with(cmd, "git-")) {
-		cmd += 4;
+	if (skip_prefix(cmd, "git-", &cmd)) {
 		argv[0] = cmd;
 		handle_builtin(argc, argv);
 		die("cannot handle %s as a builtin", cmd);
@@ -635,8 +633,8 @@ int main(int argc, char **av)
 	argc--;
 	handle_options(&argv, &argc, NULL);
 	if (argc > 0) {
-		if (starts_with(argv[0], "--"))
-			argv[0] += 2;
+		/* translate --help and --version into commands */
+		skip_prefix(argv[0], "--", &argv[0]);
 	} else {
 		/* The user didn't specify a command; give them help */
 		commit_pager_choice();
diff --git a/help.c b/help.c
index b266b09320..f31f29ac42 100644
--- a/help.c
+++ b/help.c
@@ -129,7 +129,6 @@ static void list_commands_in_dir(struct cmdnames *cmds,
 					 const char *path,
 					 const char *prefix)
 {
-	int prefix_len;
 	DIR *dir = opendir(path);
 	struct dirent *de;
 	struct strbuf buf = STRBUF_INIT;
@@ -139,15 +138,15 @@ static void list_commands_in_dir(struct cmdnames *cmds,
 		return;
 	if (!prefix)
 		prefix = "git-";
-	prefix_len = strlen(prefix);
 
 	strbuf_addf(&buf, "%s/", path);
 	len = buf.len;
 
 	while ((de = readdir(dir)) != NULL) {
+		const char *ent;
 		int entlen;
 
-		if (!starts_with(de->d_name, prefix))
+		if (!skip_prefix(de->d_name, prefix, &ent))
 			continue;
 
 		strbuf_setlen(&buf, len);
@@ -155,11 +154,11 @@ static void list_commands_in_dir(struct cmdnames *cmds,
 		if (!is_executable(buf.buf))
 			continue;
 
-		entlen = strlen(de->d_name) - prefix_len;
-		if (has_extension(de->d_name, ".exe"))
+		entlen = strlen(ent);
+		if (has_extension(ent, ".exe"))
 			entlen -= 4;
 
-		add_cmdname(cmds, de->d_name + prefix_len, entlen);
+		add_cmdname(cmds, ent, entlen);
 	}
 	closedir(dir);
 	strbuf_release(&buf);
@@ -251,11 +250,13 @@ static struct cmdnames aliases;
 
 static int git_unknown_cmd_config(const char *var, const char *value, void *cb)
 {
+	const char *p;
+
 	if (!strcmp(var, "help.autocorrect"))
 		autocorrect = git_config_int(var,value);
 	/* Also use aliases for command lookup */
-	if (starts_with(var, "alias."))
-		add_cmdname(&aliases, var + 6, strlen(var + 6));
+	if (skip_prefix(var, "alias.", &p))
+		add_cmdname(&aliases, p, strlen(p));
 
 	return git_default_config(var, value, cb);
 }
@@ -412,11 +413,12 @@ static int append_similar_ref(const char *refname, const unsigned char *sha1,
 {
 	struct similar_ref_cb *cb = (struct similar_ref_cb *)(cb_data);
 	char *branch = strrchr(refname, '/') + 1;
+	const char *remote;
+
 	/* A remote branch of the same name is deemed similar */
-	if (starts_with(refname, "refs/remotes/") &&
+	if (skip_prefix(refname, "refs/remotes/", &remote) &&
 	    !strcmp(branch, cb->base_ref))
-		string_list_append(cb->similar_refs,
-				   refname + strlen("refs/remotes/"));
+		string_list_append(cb->similar_refs, remote);
 	return 0;
 }
 
diff --git a/http-backend.c b/http-backend.c
index d2c0a625ce..57290d9bda 100644
--- a/http-backend.c
+++ b/http-backend.c
@@ -221,17 +221,19 @@ static void get_idx_file(char *name)
 
 static int http_config(const char *var, const char *value, void *cb)
 {
+	const char *p;
+
 	if (!strcmp(var, "http.getanyfile")) {
 		getanyfile = git_config_bool(var, value);
 		return 0;
 	}
 
-	if (starts_with(var, "http.")) {
+	if (skip_prefix(var, "http.", &p)) {
 		int i;
 
 		for (i = 0; i < ARRAY_SIZE(rpc_service); i++) {
 			struct rpc_service *svc = &rpc_service[i];
-			if (!strcmp(var + 5, svc->config_name)) {
+			if (!strcmp(p, svc->config_name)) {
 				svc->enabled = git_config_bool(var, value);
 				return 0;
 			}
@@ -244,15 +246,16 @@ static int http_config(const char *var, const char *value, void *cb)
 
 static struct rpc_service *select_service(const char *name)
 {
+	const char *svc_name;
 	struct rpc_service *svc = NULL;
 	int i;
 
-	if (!starts_with(name, "git-"))
+	if (!skip_prefix(name, "git-", &svc_name))
 		forbidden("Unsupported service: '%s'", name);
 
 	for (i = 0; i < ARRAY_SIZE(rpc_service); i++) {
 		struct rpc_service *s = &rpc_service[i];
-		if (!strcmp(s->name, name + 4)) {
+		if (!strcmp(s->name, svc_name)) {
 			svc = s;
 			break;
 		}
diff --git a/http-push.c b/http-push.c
index de00d1693a..c5c95e85ea 100644
--- a/http-push.c
+++ b/http-push.c
@@ -719,14 +719,10 @@ static int fetch_indices(void)
 	return ret;
 }
 
-static void one_remote_object(const char *hex)
+static void one_remote_object(const unsigned char *sha1)
 {
-	unsigned char sha1[20];
 	struct object *obj;
 
-	if (get_sha1_hex(hex, sha1) != 0)
-		return;
-
 	obj = lookup_object(sha1);
 	if (!obj)
 		obj = parse_object(sha1);
@@ -770,9 +766,9 @@ static void handle_new_lock_ctx(struct xml_ctx *ctx, int tag_closed)
 			lock->owner = xmalloc(strlen(ctx->cdata) + 1);
 			strcpy(lock->owner, ctx->cdata);
 		} else if (!strcmp(ctx->name, DAV_ACTIVELOCK_TIMEOUT)) {
-			if (starts_with(ctx->cdata, "Second-"))
-				lock->timeout =
-					strtol(ctx->cdata + 7, NULL, 10);
+			const char *arg;
+			if (skip_prefix(ctx->cdata, "Second-", &arg))
+				lock->timeout = strtol(arg, NULL, 10);
 		} else if (!strcmp(ctx->name, DAV_ACTIVELOCK_TOKEN)) {
 			lock->token = xmalloc(strlen(ctx->cdata) + 1);
 			strcpy(lock->token, ctx->cdata);
@@ -1020,26 +1016,38 @@ static void remote_ls(const char *path, int flags,
 		      void (*userFunc)(struct remote_ls_ctx *ls),
 		      void *userData);
 
+/* extract hex from sharded "xx/x{40}" filename */
+static int get_sha1_hex_from_objpath(const char *path, unsigned char *sha1)
+{
+	char hex[40];
+
+	if (strlen(path) != 41)
+		return -1;
+
+	memcpy(hex, path, 2);
+	path += 2;
+	path++; /* skip '/' */
+	memcpy(hex, path, 38);
+
+	return get_sha1_hex(hex, sha1);
+}
+
 static void process_ls_object(struct remote_ls_ctx *ls)
 {
 	unsigned int *parent = (unsigned int *)ls->userData;
-	char *path = ls->dentry_name;
-	char *obj_hex;
+	const char *path = ls->dentry_name;
+	unsigned char sha1[20];
 
 	if (!strcmp(ls->path, ls->dentry_name) && (ls->flags & IS_DIR)) {
 		remote_dir_exists[*parent] = 1;
 		return;
 	}
 
-	if (strlen(path) != 49)
+	if (!skip_prefix(path, "objects/", &path) ||
+	    get_sha1_hex_from_objpath(path, sha1))
 		return;
-	path += 8;
-	obj_hex = xmalloc(strlen(path));
-	/* NB: path is not null-terminated, can not use strlcpy here */
-	memcpy(obj_hex, path, 2);
-	strcpy(obj_hex + 2, path + 3);
-	one_remote_object(obj_hex);
-	free(obj_hex);
+
+	one_remote_object(sha1);
 }
 
 static void process_ls_ref(struct remote_ls_ctx *ls)
@@ -1561,6 +1569,7 @@ static void fetch_symref(const char *path, char **symref, unsigned char *sha1)
 {
 	char *url;
 	struct strbuf buffer = STRBUF_INIT;
+	const char *name;
 
 	url = xmalloc(strlen(repo->url) + strlen(path) + 1);
 	sprintf(url, "%s%s", repo->url, path);
@@ -1578,8 +1587,8 @@ static void fetch_symref(const char *path, char **symref, unsigned char *sha1)
 		return;
 
 	/* If it's a symref, set the refname; otherwise try for a sha1 */
-	if (starts_with((char *)buffer.buf, "ref: ")) {
-		*symref = xmemdupz((char *)buffer.buf + 5, buffer.len - 6);
+	if (skip_prefix(buffer.buf, "ref: ", &name)) {
+		*symref = xmemdupz(name, buffer.len - (name - buffer.buf));
 	} else {
 		get_sha1_hex(buffer.buf, sha1);
 	}
diff --git a/http.c b/http.c
index 3a28b219be..c8cd50dd0c 100644
--- a/http.c
+++ b/http.c
@@ -1087,11 +1087,10 @@ static int update_url_from_redirect(struct strbuf *base,
 	if (!strcmp(asked, got->buf))
 		return 0;
 
-	if (!starts_with(asked, base->buf))
+	if (!skip_prefix(asked, base->buf, &tail))
 		die("BUG: update_url_from_redirect: %s is not a superset of %s",
 		    asked, base->buf);
 
-	tail = asked + base->len;
 	tail_len = strlen(tail);
 
 	if (got->len < tail_len ||
diff --git a/imap-send.c b/imap-send.c
index 83a6ed2ac3..524fbabc96 100644
--- a/imap-send.c
+++ b/imap-send.c
@@ -1328,13 +1328,9 @@ static char *imap_folder;
 
 static int git_imap_config(const char *key, const char *val, void *cb)
 {
-	char imap_key[] = "imap.";
-
-	if (strncmp(key, imap_key, sizeof imap_key - 1))
+	if (!skip_prefix(key, "imap.", &key))
 		return 0;
 
-	key += sizeof imap_key - 1;
-
 	/* check booleans first, and barf on others */
 	if (!strcmp("sslverify", key))
 		server.ssl_verify = git_config_bool(key, val);
diff --git a/merge-recursive.c b/merge-recursive.c
index d38a3b2eb5..e6e1fa33fd 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -2065,6 +2065,8 @@ void init_merge_options(struct merge_options *o)
 
 int parse_merge_opt(struct merge_options *o, const char *s)
 {
+	const char *arg;
+
 	if (!s || !*s)
 		return -1;
 	if (!strcmp(s, "ours"))
@@ -2073,14 +2075,14 @@ int parse_merge_opt(struct merge_options *o, const char *s)
 		o->recursive_variant = MERGE_RECURSIVE_THEIRS;
 	else if (!strcmp(s, "subtree"))
 		o->subtree_shift = "";
-	else if (starts_with(s, "subtree="))
-		o->subtree_shift = s + strlen("subtree=");
+	else if (skip_prefix(s, "subtree=", &arg))
+		o->subtree_shift = arg;
 	else if (!strcmp(s, "patience"))
 		o->xdl_opts = DIFF_WITH_ALG(o, PATIENCE_DIFF);
 	else if (!strcmp(s, "histogram"))
 		o->xdl_opts = DIFF_WITH_ALG(o, HISTOGRAM_DIFF);
-	else if (starts_with(s, "diff-algorithm=")) {
-		long value = parse_algorithm_value(s + strlen("diff-algorithm="));
+	else if (skip_prefix(s, "diff-algorithm=", &arg)) {
+		long value = parse_algorithm_value(arg);
 		if (value < 0)
 			return -1;
 		/* clear out previous settings */
@@ -2098,9 +2100,8 @@ int parse_merge_opt(struct merge_options *o, const char *s)
 		o->renormalize = 1;
 	else if (!strcmp(s, "no-renormalize"))
 		o->renormalize = 0;
-	else if (starts_with(s, "rename-threshold=")) {
-		const char *score = s + strlen("rename-threshold=");
-		if ((o->rename_score = parse_rename_score(&score)) == -1 || *score != 0)
+	else if (skip_prefix(s, "rename-threshold=", &arg)) {
+		if ((o->rename_score = parse_rename_score(&arg)) == -1 || *arg != 0)
 			return -1;
 	}
 	else
diff --git a/parse-options.c b/parse-options.c
index b536896f26..e7dafa80d5 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -231,7 +231,8 @@ static int parse_long_opt(struct parse_opt_ctx_t *p, const char *arg,
 			continue;
 
 again:
-		rest = skip_prefix(arg, long_name);
+		if (!skip_prefix(arg, long_name, &rest))
+			rest = NULL;
 		if (options->type == OPTION_ARGUMENT) {
 			if (!rest)
 				continue;
@@ -280,12 +281,13 @@ is_abbreviated:
 				continue;
 			}
 			flags |= OPT_UNSET;
-			rest = skip_prefix(arg + 3, long_name);
-			/* abbreviated and negated? */
-			if (!rest && starts_with(long_name, arg + 3))
-				goto is_abbreviated;
-			if (!rest)
-				continue;
+			if (!skip_prefix(arg + 3, long_name, &rest)) {
+				/* abbreviated and negated? */
+				if (starts_with(long_name, arg + 3))
+					goto is_abbreviated;
+				else
+					continue;
+			}
 		}
 		if (*rest) {
 			if (*rest != '=')
diff --git a/pretty.c b/pretty.c
index c93c14b080..b5cf3d52c3 100644
--- a/pretty.c
+++ b/pretty.c
@@ -40,10 +40,9 @@ static int git_pretty_formats_config(const char *var, const char *value, void *c
 	const char *fmt;
 	int i;
 
-	if (!starts_with(var, "pretty."))
+	if (!skip_prefix(var, "pretty.", &name))
 		return 0;
 
-	name = var + strlen("pretty.");
 	for (i = 0; i < builtin_formats_len; i++) {
 		if (!strcmp(commit_formats[i].name, name))
 			return 0;
diff --git a/remote-curl.c b/remote-curl.c
index 4493b389de..cdcca2903b 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -791,9 +791,9 @@ static void parse_fetch(struct strbuf *buf)
 	int alloc_heads = 0, nr_heads = 0;
 
 	do {
-		if (starts_with(buf->buf, "fetch ")) {
-			char *p = buf->buf + strlen("fetch ");
-			char *name;
+		const char *p;
+		if (skip_prefix(buf->buf, "fetch ", &p)) {
+			const char *name;
 			struct ref *ref;
 			unsigned char old_sha1[20];
 
@@ -968,6 +968,8 @@ int main(int argc, const char **argv)
 	http_init(remote, url.buf, 0);
 
 	do {
+		const char *arg;
+
 		if (strbuf_getline(&buf, stdin, '\n') == EOF) {
 			if (ferror(stdin))
 				fprintf(stderr, "Error reading command stream\n");
@@ -989,9 +991,8 @@ int main(int argc, const char **argv)
 		} else if (starts_with(buf.buf, "push ")) {
 			parse_push(&buf);
 
-		} else if (starts_with(buf.buf, "option ")) {
-			char *name = buf.buf + strlen("option ");
-			char *value = strchr(name, ' ');
+		} else if (skip_prefix(buf.buf, "option ", &arg)) {
+			char *value = strchr(arg, ' ');
 			int result;
 
 			if (value)
@@ -999,7 +1000,7 @@ int main(int argc, const char **argv)
 			else
 				value = "true";
 
-			result = set_option(name, value);
+			result = set_option(arg, value);
 			if (!result)
 				printf("ok\n");
 			else if (result < 0)
diff --git a/remote.c b/remote.c
index ae04043203..a0c6ccf5b2 100644
--- a/remote.c
+++ b/remote.c
@@ -488,9 +488,8 @@ static void read_config(void)
 	current_branch = NULL;
 	head_ref = resolve_ref_unsafe("HEAD", sha1, 0, &flag);
 	if (head_ref && (flag & REF_ISSYMREF) &&
-	    starts_with(head_ref, "refs/heads/")) {
-		current_branch =
-			make_branch(head_ref + strlen("refs/heads/"), 0);
+	    skip_prefix(head_ref, "refs/heads/", &head_ref)) {
+		current_branch = make_branch(head_ref, 0);
 	}
 	git_config(handle_config, NULL);
 	if (branch_pushremote_name) {
diff --git a/sha1_name.c b/sha1_name.c
index c2c938c4e1..a91e0c924b 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -901,10 +901,8 @@ static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 	const char *match = NULL, *target = NULL;
 	size_t len;
 
-	if (starts_with(message, "checkout: moving from ")) {
-		match = message + strlen("checkout: moving from ");
+	if (skip_prefix(message, "checkout: moving from ", &match))
 		target = strstr(match, " to ");
-	}
 
 	if (!match || !target)
 		return 0;
diff --git a/transport-helper.c b/transport-helper.c
index 84c616f180..3d8fe7d801 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -153,7 +153,7 @@ static struct child_process *get_helper(struct transport *transport)
 	write_constant(helper->in, "capabilities\n");
 
 	while (1) {
-		const char *capname;
+		const char *capname, *arg;
 		int mandatory = 0;
 		if (recvline(data, &buf))
 			exit(128);
@@ -183,19 +183,19 @@ static struct child_process *get_helper(struct transport *transport)
 			data->export = 1;
 		else if (!strcmp(capname, "check-connectivity"))
 			data->check_connectivity = 1;
-		else if (!data->refspecs && starts_with(capname, "refspec ")) {
+		else if (!data->refspecs && skip_prefix(capname, "refspec ", &arg)) {
 			ALLOC_GROW(refspecs,
 				   refspec_nr + 1,
 				   refspec_alloc);
-			refspecs[refspec_nr++] = xstrdup(capname + strlen("refspec "));
+			refspecs[refspec_nr++] = xstrdup(arg);
 		} else if (!strcmp(capname, "connect")) {
 			data->connect = 1;
 		} else if (!strcmp(capname, "signed-tags")) {
 			data->signed_tags = 1;
-		} else if (starts_with(capname, "export-marks ")) {
-			data->export_marks = xstrdup(capname + strlen("export-marks "));
-		} else if (starts_with(capname, "import-marks")) {
-			data->import_marks = xstrdup(capname + strlen("import-marks "));
+		} else if (skip_prefix(capname, "export-marks ", &arg)) {
+			data->export_marks = xstrdup(arg);
+		} else if (skip_prefix(capname, "import-marks ", &arg)) {
+			data->import_marks = xstrdup(arg);
 		} else if (starts_with(capname, "no-private-update")) {
 			data->no_private_update = 1;
 		} else if (mandatory) {
diff --git a/transport.c b/transport.c
index 325f03e1ee..59c9727d8d 100644
--- a/transport.c
+++ b/transport.c
@@ -192,7 +192,9 @@ static void set_upstreams(struct transport *transport, struct ref *refs,
 
 static const char *rsync_url(const char *url)
 {
-	return !starts_with(url, "rsync://") ? skip_prefix(url, "rsync:") : url;
+	if (!starts_with(url, "rsync://"))
+		skip_prefix(url, "rsync:", &url);
+	return url;
 }
 
 static struct ref *get_refs_via_rsync(struct transport *transport, int for_push)
diff --git a/urlmatch.c b/urlmatch.c
index ec87cba750..3d4c54b5cd 100644
--- a/urlmatch.c
+++ b/urlmatch.c
@@ -483,8 +483,7 @@ int urlmatch_config_entry(const char *var, const char *value, void *cb)
 	int user_matched = 0;
 	int retval;
 
-	key = skip_prefix(var, collect->section);
-	if (!key || *(key++) != '.') {
+	if (!skip_prefix(var, collect->section, &key) || *(key++) != '.') {
 		if (collect->cascade_fn)
 			return collect->cascade_fn(var, value, cb);
 		return 0; /* not interested */