Merge branch 'jk/ident-gecos-strbuf'

Fixes quite a lot of brokenness when ident information needs to be taken
from the system and cleans up the code.

By Jeff King
* jk/ident-gecos-strbuf: (22 commits)
  format-patch: do not use bogus email addresses in message ids
  ident: reject bogus email addresses with IDENT_STRICT
  ident: rename IDENT_ERROR_ON_NO_NAME to IDENT_STRICT
  format-patch: use GIT_COMMITTER_EMAIL in message ids
  ident: let callers omit name with fmt_indent
  ident: refactor NO_DATE flag in fmt_ident
  ident: reword empty ident error message
  format-patch: refactor get_patch_filename
  ident: trim whitespace from default name/email
  ident: use a dynamic strbuf in fmt_ident
  ident: use full dns names to generate email addresses
  ident: report passwd errors with a more friendly message
  drop length limitations on gecos-derived names and emails
  ident: don't write fallback username into git_default_name
  fmt_ident: drop IDENT_WARN_ON_NO_NAME code
  format-patch: use default email for generating message ids
  ident: trim trailing newline from /etc/mailname
  move git_default_* variables to ident.c
  move identity config parsing to ident.c
  fmt-merge-msg: don't use static buffer in record_person
  ...

19 files changed, 176 insertions, 238 deletions

diff --git a/Documentation/git-commit-tree.txt b/Documentation/git-commit-tree.txt
index cfb9906bb5..eb8ee9999e 100644
--- a/Documentation/git-commit-tree.txt
+++ b/Documentation/git-commit-tree.txt
@@ -88,15 +88,6 @@ for one to be entered and terminated with ^D.
 
 include::date-formats.txt[]
 
-Diagnostics
------------
-You don't exist. Go away!::
-    The passwd(5) gecos field couldn't be read
-Your parents must have hated you!::
-    The passwd(5) gecos field is longer than a giant static buffer.
-Your sysadmin must hate you!::
-    The passwd(5) name field is longer than a giant static buffer.
-
 Discussion
 ----------
 
diff --git a/Documentation/git-var.txt b/Documentation/git-var.txt
index 988a3234f4..67edf58689 100644
--- a/Documentation/git-var.txt
+++ b/Documentation/git-var.txt
@@ -59,15 +59,6 @@ ifdef::git-default-pager[]
     The build you are using chose '{git-default-pager}' as the default.
 endif::git-default-pager[]
 
-Diagnostics
------------
-You don't exist. Go away!::
-    The passwd(5) gecos field couldn't be read
-Your parents must have hated you!::
-    The passwd(5) gecos field is longer than a giant static buffer.
-Your sysadmin must hate you!::
-    The passwd(5) name field is longer than a giant static buffer.
-
 SEE ALSO
 --------
 linkgit:git-commit-tree[1]
diff --git a/builtin/commit.c b/builtin/commit.c
index a2ec73d738..f43eaafb3b 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -526,8 +526,7 @@ static void determine_author_info(struct strbuf *author_ident)
 
 	if (force_date)
 		date = force_date;
-	strbuf_addstr(author_ident, fmt_ident(name, email, date,
-					      IDENT_ERROR_ON_NO_NAME));
+	strbuf_addstr(author_ident, fmt_ident(name, email, date, IDENT_STRICT));
 	if (!split_ident_line(&author, author_ident->buf, author_ident->len)) {
 		export_one("GIT_AUTHOR_NAME", author.name_begin, author.name_end, 0);
 		export_one("GIT_AUTHOR_EMAIL", author.mail_begin, author.mail_end, 0);
diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index d42015d867..bf93b043b7 100644
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -230,7 +230,7 @@ static void add_branch_desc(struct strbuf *out, const char *name)
 static void record_person(int which, struct string_list *people,
 			  struct commit *commit)
 {
-	char name_buf[MAX_GITNAME], *name, *name_end;
+	char *name_buf, *name, *name_end;
 	struct string_list_item *elem;
 	const char *field = (which == 'a') ? "\nauthor " : "\ncommitter ";
 
@@ -243,10 +243,9 @@ static void record_person(int which, struct string_list *people,
 		name_end--;
 	while (isspace(*name_end) && name <= name_end)
 		name_end--;
-	if (name_end < name || name + MAX_GITNAME <= name_end)
+	if (name_end < name)
 		return;
-	memcpy(name_buf, name, name_end - name + 1);
-	name_buf[name_end - name + 1] = '\0';
+	name_buf = xmemdupz(name, name_end - name + 1);
 
 	elem = string_list_lookup(people, name_buf);
 	if (!elem) {
@@ -254,6 +253,7 @@ static void record_person(int which, struct string_list *people,
 		elem->util = (void *)0;
 	}
 	elem->util = (void*)(util_as_integral(elem) + 1);
+	free(name_buf);
 }
 
 static int cmp_string_list_util_as_integral(const void *a_, const void *b_)
diff --git a/builtin/log.c b/builtin/log.c
index 690caa7830..906dca475a 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -663,7 +663,8 @@ static FILE *realstdout = NULL;
 static const char *output_directory = NULL;
 static int outdir_offset;
 
-static int reopen_stdout(struct commit *commit, struct rev_info *rev, int quiet)
+static int reopen_stdout(struct commit *commit, const char *subject,
+			 struct rev_info *rev, int quiet)
 {
 	struct strbuf filename = STRBUF_INIT;
 	int suffix_len = strlen(fmt_patch_suffix) + 1;
@@ -677,7 +678,7 @@ static int reopen_stdout(struct commit *commit, struct rev_info *rev, int quiet)
 			strbuf_addch(&filename, '/');
 	}
 
-	get_patch_filename(commit, rev->nr, fmt_patch_suffix, &filename);
+	get_patch_filename(commit, subject, rev->nr, fmt_patch_suffix, &filename);
 
 	if (!quiet)
 		fprintf(realstdout, "%s\n", filename.buf + outdir_offset);
@@ -737,15 +738,10 @@ static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids, const cha
 
 static void gen_message_id(struct rev_info *info, char *base)
 {
-	const char *committer = git_committer_info(IDENT_WARN_ON_NO_NAME);
-	const char *email_start = strrchr(committer, '<');
-	const char *email_end = strrchr(committer, '>');
 	struct strbuf buf = STRBUF_INIT;
-	if (!email_start || !email_end || email_start > email_end - 1)
-		die(_("Could not extract email from committer identity."));
-	strbuf_addf(&buf, "%s.%lu.git.%.*s", base,
+	strbuf_addf(&buf, "%s.%lu.git.%s", base,
 		    (unsigned long) time(NULL),
-		    (int)(email_end - email_start - 1), email_start + 1);
+		    git_committer_info(IDENT_NO_NAME|IDENT_NO_DATE|IDENT_STRICT));
 	info->message_id = strbuf_detach(&buf, NULL);
 }
 
@@ -784,7 +780,6 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	const char *encoding = "UTF-8";
 	struct diff_options opts;
 	int need_8bit_cte = 0;
-	struct commit *commit = NULL;
 	struct pretty_print_context pp = {0};
 
 	if (rev->commit_format != CMIT_FMT_EMAIL)
@@ -792,31 +787,10 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 
 	committer = git_committer_info(0);
 
-	if (!numbered_files) {
-		/*
-		 * We fake a commit for the cover letter so we get the filename
-		 * desired.
-		 */
-		commit = xcalloc(1, sizeof(*commit));
-		commit->buffer = xmalloc(400);
-		snprintf(commit->buffer, 400,
-			"tree 0000000000000000000000000000000000000000\n"
-			"parent %s\n"
-			"author %s\n"
-			"committer %s\n\n"
-			"cover letter\n",
-			sha1_to_hex(head->object.sha1), committer, committer);
-	}
-
-	if (!use_stdout && reopen_stdout(commit, rev, quiet))
+	if (!use_stdout &&
+	    reopen_stdout(NULL, numbered_files ? NULL : "cover-letter", rev, quiet))
 		return;
 
-	if (commit) {
-
-		free(commit->buffer);
-		free(commit);
-	}
-
 	log_write_email_headers(rev, head, &pp.subject, &pp.after_subject,
 				&need_8bit_cte);
 
@@ -1173,7 +1147,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	if (do_signoff) {
 		const char *committer;
 		const char *endpos;
-		committer = git_committer_info(IDENT_ERROR_ON_NO_NAME);
+		committer = git_committer_info(IDENT_STRICT);
 		endpos = strchr(committer, '>');
 		if (!endpos)
 			die(_("bogus committer info %s"), committer);
@@ -1411,8 +1385,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			gen_message_id(&rev, sha1_to_hex(commit->object.sha1));
 		}
 
-		if (!use_stdout && reopen_stdout(numbered_files ? NULL : commit,
-						 &rev, quiet))
+		if (!use_stdout &&
+		    reopen_stdout(numbered_files ? NULL : commit, NULL, &rev, quiet))
 			die(_("Failed to create output files"));
 		shown = log_tree_commit(&rev, commit);
 		free(commit->buffer);
diff --git a/builtin/merge.c b/builtin/merge.c
index 470fc57c5d..dd50a0c57b 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -1447,7 +1447,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		refresh_cache(REFRESH_QUIET);
 		if (allow_trivial && !fast_forward_only) {
 			/* See if it is really trivial. */
-			git_committer_info(IDENT_ERROR_ON_NO_NAME);
+			git_committer_info(IDENT_STRICT);
 			printf(_("Trying really trivial in-index merge...\n"));
 			if (!read_tree_trivial(common->item->object.sha1,
 					       head_commit->object.sha1,
@@ -1490,7 +1490,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		die(_("Not possible to fast-forward, aborting."));
 
 	/* We are going to make a new commit. */
-	git_committer_info(IDENT_ERROR_ON_NO_NAME);
+	git_committer_info(IDENT_STRICT);
 
 	/*
 	 * At this point, we need a real merge.  No matter what strategy
diff --git a/builtin/tag.c b/builtin/tag.c
index 4fb6bd7b3d..7b1be85e48 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -332,7 +332,7 @@ static void create_tag(const unsigned char *object, const char *tag,
 			  sha1_to_hex(object),
 			  typename(type),
 			  tag,
-			  git_committer_info(IDENT_ERROR_ON_NO_NAME));
+			  git_committer_info(IDENT_STRICT));
 
 	if (header_len > sizeof(header_buf) - 1)
 		die(_("tag header too big."));
diff --git a/builtin/var.c b/builtin/var.c
index 99d068a532..aedbb53a2d 100644
--- a/builtin/var.c
+++ b/builtin/var.c
@@ -11,7 +11,7 @@ static const char *editor(int flag)
 {
 	const char *pgm = git_editor();
 
-	if (!pgm && flag & IDENT_ERROR_ON_NO_NAME)
+	if (!pgm && flag & IDENT_STRICT)
 		die("Terminal is dumb, but EDITOR unset");
 
 	return pgm;
@@ -55,7 +55,7 @@ static const char *read_var(const char *var)
 	val = NULL;
 	for (ptr = git_vars; ptr->read; ptr++) {
 		if (strcmp(var, ptr->name) == 0) {
-			val = ptr->read(IDENT_ERROR_ON_NO_NAME);
+			val = ptr->read(IDENT_STRICT);
 			break;
 		}
 	}
diff --git a/cache.h b/cache.h
index cc5048c202..06413e1584 100644
--- a/cache.h
+++ b/cache.h
@@ -887,15 +887,19 @@ unsigned long approxidate_careful(const char *, int *);
 unsigned long approxidate_relative(const char *date, const struct timeval *now);
 enum date_mode parse_date_format(const char *format);
 
-#define IDENT_WARN_ON_NO_NAME  1
-#define IDENT_ERROR_ON_NO_NAME 2
-#define IDENT_NO_DATE	       4
+#define IDENT_STRICT	       1
+#define IDENT_NO_DATE	       2
+#define IDENT_NO_NAME	       4
 extern const char *git_author_info(int);
 extern const char *git_committer_info(int);
 extern const char *fmt_ident(const char *name, const char *email, const char *date_str, int);
 extern const char *fmt_name(const char *name, const char *email);
+extern const char *ident_default_name(void);
+extern const char *ident_default_email(void);
+extern const char *ident_default_date(void);
 extern const char *git_editor(void);
 extern const char *git_pager(int stdout_is_tty);
+extern int git_ident_config(const char *, const char *, void *);
 
 struct ident_split {
 	const char *name_begin;
@@ -1139,9 +1143,6 @@ struct config_include_data {
 #define CONFIG_INCLUDE_INIT { 0 }
 extern int git_config_include(const char *name, const char *value, void *data);
 
-#define MAX_GITNAME (1000)
-extern char git_default_email[MAX_GITNAME];
-extern char git_default_name[MAX_GITNAME];
 #define IDENT_NAME_GIVEN 01
 #define IDENT_MAIL_GIVEN 02
 #define IDENT_ALL_GIVEN (IDENT_NAME_GIVEN|IDENT_MAIL_GIVEN)
diff --git a/commit.c b/commit.c
index 9ed36c7db5..8248a994a5 100644
--- a/commit.c
+++ b/commit.c
@@ -1154,9 +1154,9 @@ int commit_tree_extended(const struct strbuf *msg, unsigned char *tree,
 
 	/* Person/date information */
 	if (!author)
-		author = git_author_info(IDENT_ERROR_ON_NO_NAME);
+		author = git_author_info(IDENT_STRICT);
 	strbuf_addf(&buffer, "author %s\n", author);
-	strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_ERROR_ON_NO_NAME));
+	strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_STRICT));
 	if (!encoding_is_utf8)
 		strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);
 
diff --git a/config.c b/config.c
index eeee986022..71ef171cab 100644
--- a/config.c
+++ b/config.c
@@ -762,28 +762,6 @@ static int git_default_core_config(const char *var, const char *value)
 	return 0;
 }
 
-static int git_default_user_config(const char *var, const char *value)
-{
-	if (!strcmp(var, "user.name")) {
-		if (!value)
-			return config_error_nonbool(var);
-		strlcpy(git_default_name, value, sizeof(git_default_name));
-		user_ident_explicitly_given |= IDENT_NAME_GIVEN;
-		return 0;
-	}
-
-	if (!strcmp(var, "user.email")) {
-		if (!value)
-			return config_error_nonbool(var);
-		strlcpy(git_default_email, value, sizeof(git_default_email));
-		user_ident_explicitly_given |= IDENT_MAIL_GIVEN;
-		return 0;
-	}
-
-	/* Add other config variables here and to Documentation/config.txt. */
-	return 0;
-}
-
 static int git_default_i18n_config(const char *var, const char *value)
 {
 	if (!strcmp(var, "i18n.commitencoding"))
@@ -870,7 +848,7 @@ int git_default_config(const char *var, const char *value, void *dummy)
 		return git_default_core_config(var, value);
 
 	if (!prefixcmp(var, "user."))
-		return git_default_user_config(var, value);
+		return git_ident_config(var, value, dummy);
 
 	if (!prefixcmp(var, "i18n."))
 		return git_default_i18n_config(var, value);
diff --git a/environment.c b/environment.c
index d7e6c65763..669e498f5a 100644
--- a/environment.c
+++ b/environment.c
@@ -11,9 +11,6 @@
 #include "refs.h"
 #include "fmt-merge-msg.h"
 
-char git_default_email[MAX_GITNAME];
-char git_default_name[MAX_GITNAME];
-int user_ident_explicitly_given;
 int trust_executable_bit = 1;
 int trust_ctime = 1;
 int has_symlinks = 1;
diff --git a/git-compat-util.h b/git-compat-util.h
index ed11ad8119..5bd9ad7d2a 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -595,4 +595,7 @@ int rmdir_or_warn(const char *path);
  */
 int remove_or_warn(unsigned int mode, const char *path);
 
+/* Get the passwd entry for the UID of the current process. */
+struct passwd *xgetpwuid_self(void);
+
 #endif
diff --git a/gpg-interface.c b/gpg-interface.c
index 09ab64aa24..0863c61800 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -30,7 +30,7 @@ const char *get_signing_key(void)
 {
 	if (configured_signing_key)
 		return configured_signing_key;
-	return git_committer_info(IDENT_ERROR_ON_NO_NAME|IDENT_NO_DATE);
+	return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 }
 
 /*
diff --git a/http-push.c b/http-push.c
index 1df7ab5670..a832ca77a3 100644
--- a/http-push.c
+++ b/http-push.c
@@ -904,7 +904,7 @@ static struct remote_lock *lock_remote(const char *path, long timeout)
 		ep = strchr(ep + 1, '/');
 	}
 
-	escaped = xml_entities(git_default_email);
+	escaped = xml_entities(ident_default_email());
 	strbuf_addf(&out_buffer.buf, LOCK_REQUEST, escaped);
 	free(escaped);
 
diff --git a/ident.c b/ident.c
index 5df094d175..443c0751bd 100644
--- a/ident.c
+++ b/ident.c
@@ -7,7 +7,10 @@
  */
 #include "cache.h"
 
+static struct strbuf git_default_name = STRBUF_INIT;
+static struct strbuf git_default_email = STRBUF_INIT;
 static char git_default_date[50];
+int user_ident_explicitly_given;
 
 #ifdef NO_GECOS_IN_PWENT
 #define get_gecos(ignored) "&"
@@ -15,42 +18,27 @@ static char git_default_date[50];
 #define get_gecos(struct_passwd) ((struct_passwd)->pw_gecos)
 #endif
 
-static void copy_gecos(const struct passwd *w, char *name, size_t sz)
+static void copy_gecos(const struct passwd *w, struct strbuf *name)
 {
-	char *src, *dst;
-	size_t len, nlen;
-
-	nlen = strlen(w->pw_name);
+	char *src;
 
 	/* Traditionally GECOS field had office phone numbers etc, separated
 	 * with commas.  Also & stands for capitalized form of the login name.
 	 */
 
-	for (len = 0, dst = name, src = get_gecos(w); len < sz; src++) {
+	for (src = get_gecos(w); *src && *src != ','; src++) {
 		int ch = *src;
-		if (ch != '&') {
-			*dst++ = ch;
-			if (ch == 0 || ch == ',')
-				break;
-			len++;
-			continue;
-		}
-		if (len + nlen < sz) {
+		if (ch != '&')
+			strbuf_addch(name, ch);
+		else {
 			/* Sorry, Mr. McDonald... */
-			*dst++ = toupper(*w->pw_name);
-			memcpy(dst, w->pw_name + 1, nlen - 1);
-			dst += nlen - 1;
-			len += nlen;
+			strbuf_addch(name, toupper(*w->pw_name));
+			strbuf_addstr(name, w->pw_name + 1);
 		}
 	}
-	if (len < sz)
-		name[len] = 0;
-	else
-		die("Your parents must have hated you!");
-
 }
 
-static int add_mailname_host(char *buf, size_t len)
+static int add_mailname_host(struct strbuf *buf)
 {
 	FILE *mailname;
 
@@ -61,7 +49,7 @@ static int add_mailname_host(char *buf, size_t len)
 				strerror(errno));
 		return -1;
 	}
-	if (!fgets(buf, len, mailname)) {
+	if (strbuf_getline(buf, mailname, '\n') == EOF) {
 		if (ferror(mailname))
 			warning("cannot read /etc/mailname: %s",
 				strerror(errno));
@@ -73,94 +61,67 @@ static int add_mailname_host(char *buf, size_t len)
 	return 0;
 }
 
-static void add_domainname(char *buf, size_t len)
+static void add_domainname(struct strbuf *out)
 {
+	char buf[1024];
 	struct hostent *he;
-	size_t namelen;
-	const char *domainname;
 
-	if (gethostname(buf, len)) {
+	if (gethostname(buf, sizeof(buf))) {
 		warning("cannot get host name: %s", strerror(errno));
-		strlcpy(buf, "(none)", len);
+		strbuf_addstr(out, "(none)");
 		return;
 	}
-	namelen = strlen(buf);
-	if (memchr(buf, '.', namelen))
-		return;
-
-	he = gethostbyname(buf);
-	buf[namelen++] = '.';
-	buf += namelen;
-	len -= namelen;
-	if (he && (domainname = strchr(he->h_name, '.')))
-		strlcpy(buf, domainname + 1, len);
+	if (strchr(buf, '.'))
+		strbuf_addstr(out, buf);
+	else if ((he = gethostbyname(buf)) && strchr(he->h_name, '.'))
+		strbuf_addstr(out, he->h_name);
 	else
-		strlcpy(buf, "(none)", len);
+		strbuf_addf(out, "%s.(none)", buf);
 }
 
-static void copy_email(const struct passwd *pw)
+static void copy_email(const struct passwd *pw, struct strbuf *email)
 {
 	/*
 	 * Make up a fake email address
 	 * (name + '@' + hostname [+ '.' + domainname])
 	 */
-	size_t len = strlen(pw->pw_name);
-	if (len > sizeof(git_default_email)/2)
-		die("Your sysadmin must hate you!");
-	memcpy(git_default_email, pw->pw_name, len);
-	git_default_email[len++] = '@';
-
-	if (!add_mailname_host(git_default_email + len,
-				sizeof(git_default_email) - len))
+	strbuf_addstr(email, pw->pw_name);
+	strbuf_addch(email, '@');
+
+	if (!add_mailname_host(email))
 		return;	/* read from "/etc/mailname" (Debian) */
-	add_domainname(git_default_email + len,
-			sizeof(git_default_email) - len);
+	add_domainname(email);
 }
 
-static void setup_ident(const char **name, const char **emailp)
+const char *ident_default_name(void)
 {
-	struct passwd *pw = NULL;
-
-	/* Get the name ("gecos") */
-	if (!*name && !git_default_name[0]) {
-		pw = getpwuid(getuid());
-		if (!pw)
-			die("You don't exist. Go away!");
-		copy_gecos(pw, git_default_name, sizeof(git_default_name));
+	if (!git_default_name.len) {
+		copy_gecos(xgetpwuid_self(), &git_default_name);
+		strbuf_trim(&git_default_name);
 	}
-	if (!*name)
-		*name = git_default_name;
+	return git_default_name.buf;
+}
 
-	if (!*emailp && !git_default_email[0]) {
+const char *ident_default_email(void)
+{
+	if (!git_default_email.len) {
 		const char *email = getenv("EMAIL");
 
 		if (email && email[0]) {
-			strlcpy(git_default_email, email,
-				sizeof(git_default_email));
+			strbuf_addstr(&git_default_email, email);
 			user_ident_explicitly_given |= IDENT_MAIL_GIVEN;
-		} else {
-			if (!pw)
-				pw = getpwuid(getuid());
-			if (!pw)
-				die("You don't exist. Go away!");
-			copy_email(pw);
-		}
+		} else
+			copy_email(xgetpwuid_self(), &git_default_email);
+		strbuf_trim(&git_default_email);
 	}
-	if (!*emailp)
-		*emailp = git_default_email;
-
-	/* And set the default date */
-	if (!git_default_date[0])
-		datestamp(git_default_date, sizeof(git_default_date));
+	return git_default_email.buf;
 }
 
-static int add_raw(char *buf, size_t size, int offset, const char *str)
+const char *ident_default_date(void)
 {
-	size_t len = strlen(str);
-	if (offset + len > size)
-		return size;
-	memcpy(buf + offset, str, len);
-	return offset + len;
+	if (!git_default_date[0])
+		datestamp(git_default_date, sizeof(git_default_date));
+	return git_default_date;
 }
 
 static int crud(unsigned char c)
@@ -181,7 +142,7 @@ static int crud(unsigned char c)
  * Copy over a string to the destination, but avoid special
  * characters ('\n', '<' and '>') and remove crud at the end
  */
-static int copy(char *buf, size_t size, int offset, const char *src)
+static void strbuf_addstr_without_crud(struct strbuf *sb, const char *src)
 {
 	size_t i, len;
 	unsigned char c;
@@ -205,19 +166,19 @@ static int copy(char *buf, size_t size, int offset, const char *src)
 	/*
 	 * Copy the rest to the buffer, but avoid the special
 	 * characters '\n' '<' and '>' that act as delimiters on
-	 * an identification line
+	 * an identification line. We can only remove crud, never add it,
+	 * so 'len' is our maximum.
 	 */
+	strbuf_grow(sb, len);
 	for (i = 0; i < len; i++) {
 		c = *src++;
 		switch (c) {
 		case '\n': case '<': case '>':
 			continue;
 		}
-		if (offset >= size)
-			return size;
-		buf[offset++] = c;
+		sb->buf[sb->len++] = c;
 	}
-	return offset;
+	sb->buf[sb->len] = '\0';
 }
 
 /*
@@ -304,57 +265,62 @@ static const char *env_hint =
 const char *fmt_ident(const char *name, const char *email,
 		      const char *date_str, int flag)
 {
-	static char buffer[1000];
+	static struct strbuf ident = STRBUF_INIT;
 	char date[50];
-	int i;
-	int error_on_no_name = (flag & IDENT_ERROR_ON_NO_NAME);
-	int warn_on_no_name = (flag & IDENT_WARN_ON_NO_NAME);
-	int name_addr_only = (flag & IDENT_NO_DATE);
+	int strict = (flag & IDENT_STRICT);
+	int want_date = !(flag & IDENT_NO_DATE);
+	int want_name = !(flag & IDENT_NO_NAME);
 
-	setup_ident(&name, &email);
+	if (want_name && !name)
+		name = ident_default_name();
+	if (!email)
+		email = ident_default_email();
 
-	if (!*name) {
+	if (want_name && !*name) {
 		struct passwd *pw;
 
-		if ((warn_on_no_name || error_on_no_name) &&
-		    name == git_default_name && env_hint) {
-			fputs(env_hint, stderr);
-			env_hint = NULL; /* warn only once */
+		if (strict) {
+			if (name == git_default_name.buf)
+				fputs(env_hint, stderr);
+			die("empty ident name (for <%s>) not allowed", email);
 		}
-		if (error_on_no_name)
-			die("empty ident %s <%s> not allowed", name, email);
-		pw = getpwuid(getuid());
-		if (!pw)
-			die("You don't exist. Go away!");
-		strlcpy(git_default_name, pw->pw_name,
-			sizeof(git_default_name));
-		name = git_default_name;
+		pw = xgetpwuid_self();
+		name = pw->pw_name;
+	}
+
+	if (strict && email == git_default_email.buf &&
+	    strstr(email, "(none)")) {
+		fputs(env_hint, stderr);
+		die("unable to auto-detect email address (got '%s')", email);
 	}
 
-	strcpy(date, git_default_date);
-	if (!name_addr_only && date_str && date_str[0]) {
-		if (parse_date(date_str, date, sizeof(date)) < 0)
-			die("invalid date format: %s", date_str);
+	if (want_date) {
+		if (date_str && date_str[0]) {
+			if (parse_date(date_str, date, sizeof(date)) < 0)
+				die("invalid date format: %s", date_str);
+		}
+		else
+			strcpy(date, ident_default_date());
 	}
 
-	i = copy(buffer, sizeof(buffer), 0, name);
-	i = add_raw(buffer, sizeof(buffer), i, " <");
-	i = copy(buffer, sizeof(buffer), i, email);
-	if (!name_addr_only) {
-		i = add_raw(buffer, sizeof(buffer), i,  "> ");
-		i = copy(buffer, sizeof(buffer), i, date);
-	} else {
-		i = add_raw(buffer, sizeof(buffer), i, ">");
+	strbuf_reset(&ident);
+	if (want_name) {
+		strbuf_addstr_without_crud(&ident, name);
+		strbuf_addstr(&ident, " <");
 	}
-	if (i >= sizeof(buffer))
-		die("Impossibly long personal identifier");
-	buffer[i] = 0;
-	return buffer;
+	strbuf_addstr_without_crud(&ident, email);
+	if (want_name)
+			strbuf_addch(&ident, '>');
+	if (want_date) {
+		strbuf_addch(&ident, ' ');
+		strbuf_addstr_without_crud(&ident, date);
+	}
+	return ident.buf;
 }
 
 const char *fmt_name(const char *name, const char *email)
 {
-	return fmt_ident(name, email, NULL, IDENT_ERROR_ON_NO_NAME | IDENT_NO_DATE);
+	return fmt_ident(name, email, NULL, IDENT_STRICT | IDENT_NO_DATE);
 }
 
 const char *git_author_info(int flag)
@@ -385,3 +351,26 @@ int user_ident_sufficiently_given(void)
 	return (user_ident_explicitly_given == IDENT_ALL_GIVEN);
 #endif
 }
+
+int git_ident_config(const char *var, const char *value, void *data)
+{
+	if (!strcmp(var, "user.name")) {
+		if (!value)
+			return config_error_nonbool(var);
+		strbuf_reset(&git_default_name);
+		strbuf_addstr(&git_default_name, value);
+		user_ident_explicitly_given |= IDENT_NAME_GIVEN;
+		return 0;
+	}
+
+	if (!strcmp(var, "user.email")) {
+		if (!value)
+			return config_error_nonbool(var);
+		strbuf_reset(&git_default_email);
+		strbuf_addstr(&git_default_email, value);
+		user_ident_explicitly_given |= IDENT_MAIL_GIVEN;
+		return 0;
+	}
+
+	return 0;
+}
diff --git a/log-tree.c b/log-tree.c
index 376d973176..c894930c18 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -299,19 +299,22 @@ static unsigned int digits_in_number(unsigned int number)
 	return result;
 }
 
-void get_patch_filename(struct commit *commit, int nr, const char *suffix,
-			struct strbuf *buf)
+void get_patch_filename(struct commit *commit, const char *subject, int nr,
+			const char *suffix, struct strbuf *buf)
 {
 	int suffix_len = strlen(suffix) + 1;
 	int start_len = buf->len;
 
-	strbuf_addf(buf, commit ? "%04d-" : "%d", nr);
-	if (commit) {
+	strbuf_addf(buf, commit || subject ? "%04d-" : "%d", nr);
+	if (commit || subject) {
 		int max_len = start_len + FORMAT_PATCH_NAME_MAX - suffix_len;
 		struct pretty_print_context ctx = {0};
-		ctx.date_mode = DATE_NORMAL;
 
-		format_commit_message(commit, "%f", buf, &ctx);
+		if (subject)
+			strbuf_addstr(buf, subject);
+		else if (commit)
+			format_commit_message(commit, "%f", buf, &ctx);
+
 		if (max_len < buf->len)
 			strbuf_setlen(buf, max_len);
 		strbuf_addstr(buf, suffix);
@@ -384,8 +387,8 @@ void log_write_email_headers(struct rev_info *opt, struct commit *commit,
 			 mime_boundary_leader, opt->mime_boundary);
 		extra_headers = subject_buffer;
 
-		get_patch_filename(opt->numbered_files ? NULL : commit, opt->nr,
-				    opt->patch_suffix, &filename);
+		get_patch_filename(opt->numbered_files ? NULL : commit, NULL,
+				   opt->nr, opt->patch_suffix, &filename);
 		snprintf(buffer, sizeof(buffer) - 1,
 			 "\n--%s%s\n"
 			 "Content-Type: text/x-patch;"
diff --git a/log-tree.h b/log-tree.h
index 5c4cf7cac3..f5ac238bba 100644
--- a/log-tree.h
+++ b/log-tree.h
@@ -21,7 +21,7 @@ void log_write_email_headers(struct rev_info *opt, struct commit *commit,
 void load_ref_decorations(int flags);
 
 #define FORMAT_PATCH_NAME_MAX 64
-void get_patch_filename(struct commit *commit, int nr, const char *suffix,
-			struct strbuf *buf);
+void get_patch_filename(struct commit *commit, const char *subject, int nr,
+			const char *suffix, struct strbuf *buf);
 
 #endif
diff --git a/wrapper.c b/wrapper.c
index 6ccd0595f4..b5e33e49c7 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -402,3 +402,15 @@ int remove_or_warn(unsigned int mode, const char *file)
 {
 	return S_ISGITLINK(mode) ? rmdir_or_warn(file) : unlink_or_warn(file);
 }
+
+struct passwd *xgetpwuid_self(void)
+{
+	struct passwd *pw;
+
+	errno = 0;
+	pw = getpwuid(getuid());
+	if (!pw)
+		die(_("unable to look up current user in the passwd file: %s"),
+		    errno ? strerror(errno) : _("no such user"));
+	return pw;
+}