Merge branch 'sd/branch-copy' into pu

"git branch" learned "-c/-C" to create and switch to a new branch
by copying an existing one.

Has a bit of interaction with mh/packed-ref-store and bw/config-h,
so perhaps needs to wait for the former to stabilize a bit more
and possibly rebasing on them.

* sd/branch-copy:
  branch: add a --copy (-c) option to go with --move (-m)
  branch: add test for -m renaming multiple config sections
  config: create a function to format section headers

10 files changed, 484 insertions, 48 deletions

diff --git a/Documentation/git-branch.txt b/Documentation/git-branch.txt
index 81bd0a7b77..94fd89ddc5 100644
--- a/Documentation/git-branch.txt
+++ b/Documentation/git-branch.txt
@@ -18,6 +18,7 @@ SYNOPSIS
 'git branch' (--set-upstream-to=<upstream> | -u <upstream>) [<branchname>]
 'git branch' --unset-upstream [<branchname>]
 'git branch' (-m | -M) [<oldbranch>] <newbranch>
+'git branch' (-c | -C) [<oldbranch>] <newbranch>
 'git branch' (-d | -D) [-r] <branchname>...
 'git branch' --edit-description [<branchname>]
 
@@ -64,6 +65,10 @@ If <oldbranch> had a corresponding reflog, it is renamed to match
 renaming. If <newbranch> exists, -M must be used to force the rename
 to happen.
 
+The `-c` and `-C` options have the exact same semantics as `-m` and
+`-M`, except instead of the branch being renamed it along with its
+config and reflog will be copied to a new name.
+
 With a `-d` or `-D` option, `<branchname>` will be deleted.  You may
 specify more than one branch for deletion.  If the branch currently
 has a reflog then the reflog will also be deleted.
@@ -104,7 +109,7 @@ OPTIONS
 	In combination with `-d` (or `--delete`), allow deleting the
 	branch irrespective of its merged status. In combination with
 	`-m` (or `--move`), allow renaming the branch even if the new
-	branch name already exists.
+	branch name already exists, the same applies for `-c` (or `--copy`).
 
 -m::
 --move::
@@ -113,6 +118,13 @@ OPTIONS
 -M::
 	Shortcut for `--move --force`.
 
+-c::
+--copy::
+	Copy a branch and the corresponding reflog.
+
+-C::
+	Shortcut for `--copy --force`.
+
 --color[=<when>]::
 	Color branches to highlight current, local, and
 	remote-tracking branches.
diff --git a/builtin/branch.c b/builtin/branch.c
index c958e93257..684f2c4f42 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -28,6 +28,7 @@ static const char * const builtin_branch_usage[] = {
 	N_("git branch [<options>] [-l] [-f] <branch-name> [<start-point>]"),
 	N_("git branch [<options>] [-r] (-d | -D) <branch-name>..."),
 	N_("git branch [<options>] (-m | -M) [<old-branch>] <new-branch>"),
+	N_("git branch [<options>] (-c | -C) [<old-branch>] <new-branch>"),
 	N_("git branch [<options>] [-r | -a] [--points-at]"),
 	N_("git branch [<options>] [-r | -a] [--format]"),
 	NULL
@@ -450,15 +451,19 @@ static void reject_rebase_or_bisect_branch(const char *target)
 	free_worktrees(worktrees);
 }
 
-static void rename_branch(const char *oldname, const char *newname, int force)
+static void copy_or_rename_branch(const char *oldname, const char *newname, int copy, int force)
 {
 	struct strbuf oldref = STRBUF_INIT, newref = STRBUF_INIT, logmsg = STRBUF_INIT;
 	struct strbuf oldsection = STRBUF_INIT, newsection = STRBUF_INIT;
 	int recovery = 0;
 	int clobber_head_ok;
 
-	if (!oldname)
-		die(_("cannot rename the current branch while not on any."));
+	if (!oldname) {
+		if (copy)
+			die(_("cannot copy the current branch while not on any."));
+		else
+			die(_("cannot rename the current branch while not on any."));
+	}
 
 	if (strbuf_check_branch_ref(&oldref, oldname)) {
 		/*
@@ -481,17 +486,33 @@ static void rename_branch(const char *oldname, const char *newname, int force)
 
 	reject_rebase_or_bisect_branch(oldref.buf);
 
-	strbuf_addf(&logmsg, "Branch: renamed %s to %s",
-		 oldref.buf, newref.buf);
+	if (copy)
+		strbuf_addf(&logmsg, "Branch: copied %s to %s",
+			    oldref.buf, newref.buf);
+	else
+		strbuf_addf(&logmsg, "Branch: renamed %s to %s",
+			    oldref.buf, newref.buf);
 
-	if (rename_ref(oldref.buf, newref.buf, logmsg.buf))
+	if (!copy && rename_ref(oldref.buf, newref.buf, logmsg.buf))
 		die(_("Branch rename failed"));
+	if (copy && copy_existing_ref(oldref.buf, newref.buf, logmsg.buf))
+		die(_("Branch copy failed"));
 
-	if (recovery)
-		warning(_("Renamed a misnamed branch '%s' away"), oldref.buf + 11);
+	if (recovery) {
+		if (copy)
+			warning(_("Copied a misnamed branch '%s' away"),
+				oldref.buf + 11);
+		else
+			warning(_("Renamed a misnamed branch '%s' away"),
+				oldref.buf + 11);
+	}
 
-	if (replace_each_worktree_head_symref(oldref.buf, newref.buf, logmsg.buf))
-		die(_("Branch renamed to %s, but HEAD is not updated!"), newname);
+	if (replace_each_worktree_head_symref(oldref.buf, newref.buf, logmsg.buf)) {
+		if (copy)
+			die(_("Branch copied to %s, but HEAD is not updated!"), newname);
+		else
+			die(_("Branch renamed to %s, but HEAD is not updated!"), newname);
+	}
 
 	strbuf_release(&logmsg);
 
@@ -499,8 +520,10 @@ static void rename_branch(const char *oldname, const char *newname, int force)
 	strbuf_release(&oldref);
 	strbuf_addf(&newsection, "branch.%s", newref.buf + 11);
 	strbuf_release(&newref);
-	if (git_config_rename_section(oldsection.buf, newsection.buf) < 0)
+	if (!copy && git_config_rename_section(oldsection.buf, newsection.buf) < 0)
 		die(_("Branch is renamed, but update of config-file failed"));
+	if (copy && strcmp(oldname, newname) && git_config_copy_section(oldsection.buf, newsection.buf) < 0)
+		die(_("Branch is copied, but update of config-file failed"));
 	strbuf_release(&oldsection);
 	strbuf_release(&newsection);
 }
@@ -538,7 +561,7 @@ static int edit_branch_description(const char *branch_name)
 
 int cmd_branch(int argc, const char **argv, const char *prefix)
 {
-	int delete = 0, rename = 0, force = 0, list = 0;
+	int delete = 0, rename = 0, copy = 0, force = 0, list = 0;
 	int reflog = 0, edit_description = 0;
 	int quiet = 0, unset_upstream = 0;
 	const char *new_upstream = NULL;
@@ -575,6 +598,8 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		OPT_BIT('D', NULL, &delete, N_("delete branch (even if not merged)"), 2),
 		OPT_BIT('m', "move", &rename, N_("move/rename a branch and its reflog"), 1),
 		OPT_BIT('M', NULL, &rename, N_("move/rename a branch, even if target exists"), 2),
+		OPT_BIT('c', "copy", &copy, N_("copy a branch and its reflog"), 1),
+		OPT_BIT('C', NULL, &copy, N_("copy a branch, even if target exists"), 2),
 		OPT_BOOL(0, "list", &list, N_("list branch names")),
 		OPT_BOOL('l', "create-reflog", &reflog, N_("create the branch's reflog")),
 		OPT_BOOL(0, "edit-description", &edit_description,
@@ -618,14 +643,14 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options, builtin_branch_usage,
 			     0);
 
-	if (!delete && !rename && !edit_description && !new_upstream && !unset_upstream && argc == 0)
+	if (!delete && !rename && !copy && !edit_description && !new_upstream && !unset_upstream && argc == 0)
 		list = 1;
 
 	if (filter.with_commit || filter.merge != REF_FILTER_MERGED_NONE || filter.points_at.nr ||
 	    filter.no_commit)
 		list = 1;
 
-	if (!!delete + !!rename + !!new_upstream +
+	if (!!delete + !!rename + !!copy + !!new_upstream +
 	    list + unset_upstream > 1)
 		usage_with_options(builtin_branch_usage, options);
 
@@ -643,6 +668,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	if (force) {
 		delete *= 2;
 		rename *= 2;
+		copy *= 2;
 	}
 
 	if (delete) {
@@ -697,13 +723,22 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 
 		if (edit_branch_description(branch_name))
 			return 1;
+	} else if (copy) {
+		if (!argc)
+			die(_("branch name required"));
+		else if (argc == 1)
+			copy_or_rename_branch(head, argv[0], 1, copy > 1);
+		else if (argc == 2)
+			copy_or_rename_branch(argv[0], argv[1], 1, copy > 1);
+		else
+			die(_("too many branches for a copy operation"));
 	} else if (rename) {
 		if (!argc)
 			die(_("branch name required"));
 		else if (argc == 1)
-			rename_branch(head, argv[0], rename > 1);
+			copy_or_rename_branch(head, argv[0], 0, rename > 1);
 		else if (argc == 2)
-			rename_branch(argv[0], argv[1], rename > 1);
+			copy_or_rename_branch(argv[0], argv[1], 0, rename > 1);
 		else
 			die(_("too many branches for a rename operation"));
 	} else if (new_upstream) {
diff --git a/config.c b/config.c
index f59c30de3a..6e5878d7af 100644
--- a/config.c
+++ b/config.c
@@ -2251,10 +2251,10 @@ static int write_error(const char *filename)
 	return 4;
 }
 
-static int store_write_section(int fd, const char *key)
+static struct strbuf store_create_section(const char *key)
 {
 	const char *dot;
-	int i, success;
+	int i;
 	struct strbuf sb = STRBUF_INIT;
 
 	dot = memchr(key, '.', store.baselen);
@@ -2270,6 +2270,15 @@ static int store_write_section(int fd, const char *key)
 		strbuf_addf(&sb, "[%.*s]\n", store.baselen, key);
 	}
 
+	return sb;
+}
+
+static int store_write_section(int fd, const char *key)
+{
+	int success;
+
+	struct strbuf sb = store_create_section(key);
+
 	success = write_in_full(fd, sb.buf, sb.len) == sb.len;
 	strbuf_release(&sb);
 
@@ -2711,8 +2720,8 @@ static int section_name_is_ok(const char *name)
 }
 
 /* if new_name == NULL, the section is removed instead */
-int git_config_rename_section_in_file(const char *config_filename,
-				      const char *old_name, const char *new_name)
+static int git_config_copy_or_rename_section_in_file(const char *config_filename,
+				      const char *old_name, const char *new_name, int copy)
 {
 	int ret = 0, remove = 0;
 	char *filename_buf = NULL;
@@ -2721,6 +2730,7 @@ int git_config_rename_section_in_file(const char *config_filename,
 	char buf[1024];
 	FILE *config_file = NULL;
 	struct stat st;
+	struct strbuf copystr = STRBUF_INIT;
 
 	if (new_name && !section_name_is_ok(new_name)) {
 		ret = error("invalid section name: %s", new_name);
@@ -2759,12 +2769,30 @@ int git_config_rename_section_in_file(const char *config_filename,
 	while (fgets(buf, sizeof(buf), config_file)) {
 		int i;
 		int length;
+		int is_section = 0;
 		char *output = buf;
 		for (i = 0; buf[i] && isspace(buf[i]); i++)
 			; /* do nothing */
 		if (buf[i] == '[') {
 			/* it's a section */
-			int offset = section_name_match(&buf[i], old_name);
+			int offset;
+			is_section = 1;
+
+			/*
+			 * When encountering a new section under -c we
+			 * need to flush out any section we're already
+			 * coping and begin anew. There might be
+			 * multiple [branch "$name"] sections.
+			 */
+			if (copystr.len > 0) {
+				if (write_in_full(out_fd, copystr.buf, copystr.len) != copystr.len) {
+					ret = write_error(get_lock_file_path(lock));
+					goto out;
+				}
+				strbuf_reset(&copystr);
+			}
+
+			offset = section_name_match(&buf[i], old_name);
 			if (offset > 0) {
 				ret++;
 				if (new_name == NULL) {
@@ -2772,25 +2800,30 @@ int git_config_rename_section_in_file(const char *config_filename,
 					continue;
 				}
 				store.baselen = strlen(new_name);
-				if (!store_write_section(out_fd, new_name)) {
-					ret = write_error(get_lock_file_path(lock));
-					goto out;
-				}
-				/*
-				 * We wrote out the new section, with
-				 * a newline, now skip the old
-				 * section's length
-				 */
-				output += offset + i;
-				if (strlen(output) > 0) {
+				if (!copy) {
+					if (!store_write_section(out_fd, new_name)) {
+						ret = write_error(get_lock_file_path(lock));
+						goto out;
+					}
+
 					/*
-					 * More content means there's
-					 * a declaration to put on the
-					 * next line; indent with a
-					 * tab
+					 * We wrote out the new section, with
+					 * a newline, now skip the old
+					 * section's length
 					 */
-					output -= 1;
-					output[0] = '\t';
+					output += offset + i;
+					if (strlen(output) > 0) {
+						/*
+						 * More content means there's
+						 * a declaration to put on the
+						 * next line; indent with a
+						 * tab
+						 */
+						output -= 1;
+						output[0] = '\t';
+					}
+				} else {
+					copystr = store_create_section(new_name);
 				}
 			}
 			remove = 0;
@@ -2798,11 +2831,30 @@ int git_config_rename_section_in_file(const char *config_filename,
 		if (remove)
 			continue;
 		length = strlen(output);
+
+		if (!is_section && copystr.len > 0) {
+			strbuf_add(&copystr, output, length);
+		}
+
 		if (write_in_full(out_fd, output, length) != length) {
 			ret = write_error(get_lock_file_path(lock));
 			goto out;
 		}
 	}
+
+	/*
+	 * Copy a trailing section at the end of the config, won't be
+	 * flushed by the usual "flush because we have a new section
+	 * logic in the loop above.
+	 */
+	if (copystr.len > 0) {
+		if (write_in_full(out_fd, copystr.buf, copystr.len) != copystr.len) {
+			ret = write_error(get_lock_file_path(lock));
+			goto out;
+		}
+		strbuf_reset(&copystr);
+	}
+
 	fclose(config_file);
 	config_file = NULL;
 commit_and_out:
@@ -2818,11 +2870,30 @@ out_no_rollback:
 	return ret;
 }
 
+int git_config_rename_section_in_file(const char *config_filename,
+				      const char *old_name, const char *new_name)
+{
+	return git_config_copy_or_rename_section_in_file(config_filename,
+					 old_name, new_name, 0);
+}
+
 int git_config_rename_section(const char *old_name, const char *new_name)
 {
 	return git_config_rename_section_in_file(NULL, old_name, new_name);
 }
 
+int git_config_copy_section_in_file(const char *config_filename,
+				      const char *old_name, const char *new_name)
+{
+	return git_config_copy_or_rename_section_in_file(config_filename,
+					 old_name, new_name, 1);
+}
+
+int git_config_copy_section(const char *old_name, const char *new_name)
+{
+	return git_config_copy_section_in_file(NULL, old_name, new_name);
+}
+
 /*
  * Call this to report error for your variable that should not
  * get a boolean value (i.e. "[my] var" means "true").
diff --git a/config.h b/config.h
index 827f2b0e4a..ad61b97b91 100644
--- a/config.h
+++ b/config.h
@@ -71,6 +71,8 @@ extern int git_config_set_multivar_in_file_gently(const char *, const char *, co
 extern void git_config_set_multivar_in_file(const char *, const char *, const char *, const char *, int);
 extern int git_config_rename_section(const char *, const char *);
 extern int git_config_rename_section_in_file(const char *, const char *, const char *);
+extern int git_config_copy_section(const char *, const char *);
+extern int git_config_copy_section_in_file(const char *, const char *, const char *);
 extern const char *git_etc_gitconfig(void);
 extern int git_env_bool(const char *, int);
 extern unsigned long git_env_ulong(const char *, unsigned long);
diff --git a/refs.c b/refs.c
index c574c76d87..d9814086c9 100644
--- a/refs.c
+++ b/refs.c
@@ -2064,3 +2064,14 @@ int rename_ref(const char *oldref, const char *newref, const char *logmsg)
 {
 	return refs_rename_ref(get_main_ref_store(), oldref, newref, logmsg);
 }
+
+int refs_copy_existing_ref(struct ref_store *refs, const char *oldref,
+		    const char *newref, const char *logmsg)
+{
+	return refs->be->copy_ref(refs, oldref, newref, logmsg);
+}
+
+int copy_existing_ref(const char *oldref, const char *newref, const char *logmsg)
+{
+	return refs_copy_existing_ref(get_main_ref_store(), oldref, newref, logmsg);
+}
diff --git a/refs.h b/refs.h
index 6daa78eb50..80da9fe389 100644
--- a/refs.h
+++ b/refs.h
@@ -443,7 +443,14 @@ char *shorten_unambiguous_ref(const char *refname, int strict);
 /** rename ref, return 0 on success **/
 int refs_rename_ref(struct ref_store *refs, const char *oldref,
 		    const char *newref, const char *logmsg);
-int rename_ref(const char *oldref, const char *newref, const char *logmsg);
+int rename_ref(const char *oldref, const char *newref,
+			const char *logmsg);
+
+/** copy ref, return 0 on success **/
+int refs_copy_existing_ref(struct ref_store *refs, const char *oldref,
+		    const char *newref, const char *logmsg);
+int copy_existing_ref(const char *oldref, const char *newref,
+			const char *logmsg);
 
 int refs_create_symref(struct ref_store *refs, const char *refname,
 		       const char *target, const char *logmsg);
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 928a655a27..923e481e06 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1254,9 +1254,9 @@ static int commit_ref_update(struct files_ref_store *refs,
 			     const struct object_id *oid, const char *logmsg,
 			     struct strbuf *err);
 
-static int files_rename_ref(struct ref_store *ref_store,
+static int files_copy_or_rename_ref(struct ref_store *ref_store,
 			    const char *oldrefname, const char *newrefname,
-			    const char *logmsg)
+			    const char *logmsg, int copy)
 {
 	struct files_ref_store *refs =
 		files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
@@ -1288,8 +1288,12 @@ static int files_rename_ref(struct ref_store *ref_store,
 	}
 
 	if (flag & REF_ISSYMREF) {
-		ret = error("refname %s is a symbolic ref, renaming it is not supported",
-			    oldrefname);
+		if (copy)
+			ret = error("refname %s is a symbolic ref, copying it is not supported",
+				    oldrefname);
+		else
+			ret = error("refname %s is a symbolic ref, renaming it is not supported",
+				    oldrefname);
 		goto out;
 	}
 	if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
@@ -1297,13 +1301,19 @@ static int files_rename_ref(struct ref_store *ref_store,
 		goto out;
 	}
 
-	if (log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
+	if (!copy && log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
 		ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
 			    oldrefname, strerror(errno));
 		goto out;
 	}
 
-	if (refs_delete_ref(&refs->base, logmsg, oldrefname,
+	if (copy && log && copy_file(tmp_renamed_log.buf, sb_oldref.buf, 0644)) {
+		ret = error("unable to copy logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
+			    oldrefname, strerror(errno));
+		goto out;
+	}
+
+	if (!copy && refs_delete_ref(&refs->base, logmsg, oldrefname,
 			    orig_oid.hash, REF_NODEREF)) {
 		error("unable to delete old %s", oldrefname);
 		goto rollback;
@@ -1316,7 +1326,7 @@ static int files_rename_ref(struct ref_store *ref_store,
 	 * the safety anyway; we want to delete the reference whatever
 	 * its current value.
 	 */
-	if (!refs_read_ref_full(&refs->base, newrefname,
+	if (!copy && !refs_read_ref_full(&refs->base, newrefname,
 				RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
 				oid.hash, NULL) &&
 	    refs_delete_ref(&refs->base, NULL, newrefname,
@@ -1347,7 +1357,10 @@ static int files_rename_ref(struct ref_store *ref_store,
 	lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
 				   REF_NODEREF, NULL, &err);
 	if (!lock) {
-		error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
+		if (copy)
+			error("unable to copy '%s' to '%s': %s", oldrefname, newrefname, err.buf);
+		else
+			error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
 		strbuf_release(&err);
 		goto rollback;
 	}
@@ -1398,6 +1411,22 @@ static int files_rename_ref(struct ref_store *ref_store,
 	return ret;
 }
 
+static int files_rename_ref(struct ref_store *ref_store,
+			    const char *oldrefname, const char *newrefname,
+			    const char *logmsg)
+{
+	return files_copy_or_rename_ref(ref_store, oldrefname,
+				 newrefname, logmsg, 0);
+}
+
+static int files_copy_ref(struct ref_store *ref_store,
+			    const char *oldrefname, const char *newrefname,
+			    const char *logmsg)
+{
+	return files_copy_or_rename_ref(ref_store, oldrefname,
+				 newrefname, logmsg, 1);
+}
+
 static int close_ref(struct ref_lock *lock)
 {
 	if (close_lock_file(lock->lk))
@@ -2908,6 +2937,7 @@ struct ref_storage_be refs_be_files = {
 	files_create_symref,
 	files_delete_refs,
 	files_rename_ref,
+	files_copy_ref,
 
 	files_ref_iterator_begin,
 	files_read_raw_ref,
diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index dc09012300..96f9141656 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -794,6 +794,13 @@ static int packed_rename_ref(struct ref_store *ref_store,
 	die("BUG: packed reference store does not support renaming references");
 }
 
+static int packed_copy_ref(struct ref_store *ref_store,
+			   const char *oldrefname, const char *newrefname,
+			   const char *logmsg)
+{
+	die("BUG: packed reference store does not support copying references");
+}
+
 static struct ref_iterator *packed_reflog_iterator_begin(struct ref_store *ref_store)
 {
 	return empty_ref_iterator_begin();
@@ -859,6 +866,7 @@ struct ref_storage_be refs_be_packed = {
 	packed_create_symref,
 	packed_delete_refs,
 	packed_rename_ref,
+	packed_copy_ref,
 
 	packed_ref_iterator_begin,
 	packed_read_raw_ref,
diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 4789106fc0..39d2f55484 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -552,6 +552,9 @@ typedef int delete_refs_fn(struct ref_store *ref_store, const char *msg,
 typedef int rename_ref_fn(struct ref_store *ref_store,
 			  const char *oldref, const char *newref,
 			  const char *logmsg);
+typedef int copy_ref_fn(struct ref_store *ref_store,
+			  const char *oldref, const char *newref,
+			  const char *logmsg);
 
 /*
  * Iterate over the references in `ref_store` whose names start with
@@ -650,6 +653,7 @@ struct ref_storage_be {
 	create_symref_fn *create_symref;
 	delete_refs_fn *delete_refs;
 	rename_ref_fn *rename_ref;
+	copy_ref_fn *copy_ref;
 
 	ref_iterator_begin_fn *iterator_begin;
 	read_raw_ref_fn *read_raw_ref;
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 9d707d2a40..35e90d0ffd 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -368,6 +368,262 @@ test_expect_success 'config information was renamed, too' '
 	test_must_fail git config branch.s/s.dummy
 '
 
+test_expect_success 'git branch -m correctly renames multiple config sections' '
+	test_when_finished "git checkout master" &&
+	git checkout -b source master &&
+
+	# Assert that a config file with multiple config sections has
+	# those sections preserved...
+	cat >expect <<-\EOF &&
+	branch.dest.key1=value1
+	some.gar.b=age
+	branch.dest.key2=value2
+	EOF
+	cat >config.branch <<\EOF &&
+;; Note the lack of -\EOF above & mixed indenting here. This is
+;; intentional, we are also testing that the formatting of copied
+;; sections is preserved.
+
+;; Comment for source. Tabs
+[branch "source"]
+	;; Comment for the source value
+	key1 = value1
+;; Comment for some.gar. Spaces
+[some "gar"]
+    ;; Comment for the some.gar value
+    b = age
+;; Comment for source, again. Mixed tabs/spaces.
+[branch "source"]
+    ;; Comment for the source value, again
+	key2 = value2
+EOF
+	cat config.branch >>.git/config &&
+	git branch -m source dest &&
+	git config -f .git/config -l | grep -F -e source -e dest -e some.gar >actual &&
+	test_cmp expect actual &&
+
+	# ...and that the comments for those sections are also
+	# preserved.
+	cat config.branch | sed "s/\"source\"/\"dest\"/" >expect &&
+	sed -n -e "/Note the lack/,\$p" .git/config >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'git branch -c dumps usage' '
+	test_expect_code 128 git branch -c 2>err &&
+	test_i18ngrep "branch name required" err
+'
+
+test_expect_success 'git branch --copy dumps usage' '
+	test_expect_code 128 git branch --copy 2>err &&
+	test_i18ngrep "branch name required" err
+'
+
+test_expect_success 'git branch -c d e should work' '
+	git branch -l d &&
+	git reflog exists refs/heads/d &&
+	git config branch.d.dummy Hello &&
+	git branch -c d e &&
+	git reflog exists refs/heads/d &&
+	git reflog exists refs/heads/e &&
+	echo Hello >expect &&
+	git config branch.e.dummy >actual &&
+	test_cmp expect actual &&
+	echo Hello >expect &&
+	git config branch.d.dummy >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'git branch --copy is a synonym for -c' '
+	git branch -l copy &&
+	git reflog exists refs/heads/copy &&
+	git config branch.copy.dummy Hello &&
+	git branch --copy copy copy-to &&
+	git reflog exists refs/heads/copy &&
+	git reflog exists refs/heads/copy-to &&
+	echo Hello >expect &&
+	git config branch.copy.dummy >actual &&
+	test_cmp expect actual &&
+	echo Hello >expect &&
+	git config branch.copy-to.dummy >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'git branch -c ee ef should copy and checkout branch ef' '
+	git checkout -b ee &&
+	git reflog exists refs/heads/ee &&
+	git config branch.ee.dummy Hello &&
+	git branch -c ee ef &&
+	git reflog exists refs/heads/ee &&
+	git reflog exists refs/heads/ef &&
+	test $(git config branch.ee.dummy) = Hello &&
+	test $(git config branch.ef.dummy) = Hello &&
+	test $(git rev-parse --abbrev-ref HEAD) = ef
+'
+
+test_expect_success 'git branch -c f/f g/g should work' '
+	git branch -l f/f &&
+	git reflog exists refs/heads/f/f &&
+	git config branch.f/f.dummy Hello &&
+	git branch -c f/f g/g &&
+	git reflog exists refs/heads/f/f &&
+	git reflog exists refs/heads/g/g &&
+	test $(git config branch.f/f.dummy) = Hello &&
+	test $(git config branch.g/g.dummy) = Hello
+'
+
+test_expect_success 'git branch -c m2 m2 should work' '
+	git branch -l m2 &&
+	git reflog exists refs/heads/m2 &&
+	git config branch.m2.dummy Hello &&
+	git branch -c m2 m2 &&
+	git reflog exists refs/heads/m2 &&
+	test $(git config branch.m2.dummy) = Hello
+'
+
+test_expect_success 'git branch -c zz zz/zz should fail' '
+	git branch -l zz &&
+	git reflog exists refs/heads/zz &&
+	test_must_fail git branch -c zz zz/zz
+'
+
+test_expect_success 'git branch -c b/b b should fail' '
+	git branch -l b/b &&
+	test_must_fail git branch -c b/b b
+'
+
+test_expect_success 'git branch -C o/q o/p should work when o/p exists' '
+	git branch -l o/q &&
+	git reflog exists refs/heads/o/q &&
+	git reflog exists refs/heads/o/p &&
+	git branch -C o/q o/p
+'
+
+test_expect_success 'git branch -c -f o/q o/p should work when o/p exists' '
+	git reflog exists refs/heads/o/q &&
+	git reflog exists refs/heads/o/p &&
+	git branch -c -f o/q o/p
+'
+
+test_expect_success 'git branch -c qq rr/qq should fail when r exists' '
+	git branch qq &&
+	git branch rr &&
+	test_must_fail git branch -c qq rr/qq
+'
+
+test_expect_success 'git branch -C b1 b2 should fail when b2 is checked out' '
+	git branch b1 &&
+	git checkout -b b2 &&
+	test_must_fail git branch -C b1 b2
+'
+
+test_expect_success 'git branch -C c1 c2 should succeed when c1 is checked out' '
+	git checkout -b c1 &&
+	git branch c2 &&
+	git branch -C c1 c2 &&
+	test $(git rev-parse --abbrev-ref HEAD) = c2
+'
+
+test_expect_success 'git branch -C c1 c2 should add entries to .git/logs/HEAD' '
+	msg="Branch: copied refs/heads/c1 to refs/heads/c2" &&
+	grep "$msg$" .git/logs/HEAD
+'
+
+test_expect_success 'git branch -C master should work when master is checked out' '
+	git checkout master &&
+	git branch -C master
+'
+
+test_expect_success 'git branch -C master master should work when master is checked out' '
+	git checkout master &&
+	git branch -C master master
+'
+
+test_expect_success 'git branch -C master5 master5 should work when master is checked out' '
+	git checkout master &&
+	git branch master5 &&
+	git branch -C master5 master5
+'
+
+test_expect_success 'git branch -C ab cd should overwrite existing config for cd' '
+	git branch -l cd &&
+	git reflog exists refs/heads/cd &&
+	git config branch.cd.dummy CD &&
+	git branch -l ab &&
+	git reflog exists refs/heads/ab &&
+	git config branch.ab.dummy AB &&
+	git branch -C ab cd &&
+	git reflog exists refs/heads/ab &&
+	git reflog exists refs/heads/cd &&
+	test $(git config branch.ab.dummy) = AB &&
+	test $(git config branch.cd.dummy) = AB
+'
+
+test_expect_success 'git branch -c correctly copies multiple config sections' '
+	FOO=1 &&
+	export FOO &&
+	test_when_finished "git checkout master" &&
+	git checkout -b source2 master &&
+
+	# Assert that a config file with multiple config sections has
+	# those sections preserved...
+	cat >expect <<-\EOF &&
+	branch.source2.key1=value1
+	branch.dest2.key1=value1
+	more.gar.b=age
+	branch.source2.key2=value2
+	branch.dest2.key2=value2
+	EOF
+	cat >config.branch <<\EOF &&
+;; Note the lack of -\EOF above & mixed indenting here. This is
+;; intentional, we are also testing that the formatting of copied
+;; sections is preserved.
+
+;; Comment for source2. Tabs
+[branch "source2"]
+	;; Comment for the source2 value
+	key1 = value1
+;; Comment for more.gar. Spaces
+[more "gar"]
+    ;; Comment for the more.gar value
+    b = age
+;; Comment for source2, again. Mixed tabs/spaces.
+[branch "source2"]
+    ;; Comment for the source2 value, again
+	key2 = value2
+EOF
+	cat config.branch >>.git/config &&
+	git branch -c source2 dest2 &&
+	git config -f .git/config -l | grep -F -e source2 -e dest2 -e more.gar >actual &&
+	test_cmp expect actual &&
+
+	# ...and that the comments and formatting for those sections
+	# is also preserved.
+	cat >expect <<\EOF &&
+;; Comment for source2. Tabs
+[branch "source2"]
+	;; Comment for the source2 value
+	key1 = value1
+;; Comment for more.gar. Spaces
+[branch "dest2"]
+	;; Comment for the source2 value
+	key1 = value1
+;; Comment for more.gar. Spaces
+[more "gar"]
+    ;; Comment for the more.gar value
+    b = age
+;; Comment for source2, again. Mixed tabs/spaces.
+[branch "source2"]
+    ;; Comment for the source2 value, again
+	key2 = value2
+[branch "dest2"]
+    ;; Comment for the source2 value, again
+	key2 = value2
+EOF
+	sed -n -e "/Comment for source2/,\$p" .git/config >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'deleting a symref' '
 	git branch target &&
 	git symbolic-ref refs/heads/symref refs/heads/target &&