[PATCH v2 08/12] init: allow overriding the default main branch name via the config

["Don Goodman-Wilson via GitGitGadget" <gitgitgadget@gmail.com>]

From: Don Goodman-Wilson <don@goodman-wilson.com>

We just introduced the command-line option `--main-branch=<branch-name>`
to allow initializing a new repository with a different initial branch
than the hard-coded one.

To allow users to override the default main branch name more permanently
(i.e. without having to specify the name manually for each and every
`git init` invocation), let's introduce the `init.defaultBranch` config
setting.

Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Don Goodman-Wilson <don@goodman-wilson.com>
---
 Documentation/config/init.txt |  4 ++++
 builtin/init-db.c             |  6 ++++--
 refs.c                        |  7 +++++--
 refs.h                        |  4 ++++
 t/t0001-init.sh               | 16 ++++++++++++++++
 5 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/Documentation/config/init.txt b/Documentation/config/init.txt
index 46fa8c6a082..6ae4a38416e 100644
--- a/Documentation/config/init.txt
+++ b/Documentation/config/init.txt
@@ -1,3 +1,7 @@
 init.templateDir::
 	Specify the directory from which templates will be copied.
 	(See the "TEMPLATE DIRECTORY" section of linkgit:git-init[1].)
+
+init.defaultBranch::
+	Allows overriding the default branch name when initializing
+	a new repository.
diff --git a/builtin/init-db.c b/builtin/init-db.c
index 287cdafaab1..d09c9dc7845 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -266,10 +266,11 @@ static int create_default_files(const char *template_path,
 	reinit = (!access(path, R_OK)
 		  || readlink(path, junk, sizeof(junk)-1) != -1);
 	if (!reinit) {
-		char *ref;
+		char *ref, *fall_back = NULL;
 
 		if (!main_branch)
-			main_branch = "master";
+			main_branch = fall_back =
+				git_main_branch_name(MAIN_BRANCH_FOR_INIT);
 
 		ref = xstrfmt("refs/heads/%s", main_branch);
 		if (check_refname_format(ref, 0) < 0)
@@ -280,6 +281,7 @@ static int create_default_files(const char *template_path,
 		free(ref);
 
 		git_config_set("core.mainbranch", main_branch);
+		free(fall_back);
 	} else if (main_branch)
 		warning(_("re-init: ignoring --main-branch=%s"), main_branch);
 
diff --git a/refs.c b/refs.c
index 7da3ac178c4..4b0e5b14062 100644
--- a/refs.c
+++ b/refs.c
@@ -563,8 +563,11 @@ void expand_ref_prefix(struct argv_array *prefixes, const char *prefix)
 char *repo_main_branch_name(struct repository *r, int flags)
 {
 	int full_name = flags & MAIN_BRANCH_FULL_NAME;
-	const char *config_key = "core.mainbranch";
-	const char *config_display_key = "core.mainBranch";
+	int for_init = flags & MAIN_BRANCH_FOR_INIT;
+	const char *config_key = for_init ?
+		 "init.defaultbranch" : "core.mainbranch";
+	const char *config_display_key = for_init ?
+		 "init.defaultBranch" : "core.mainBranch";
 	const char *fall_back = "master";
 	char *name = NULL, *ret;
 
diff --git a/refs.h b/refs.h
index 96472f9a9f5..c801d08490c 100644
--- a/refs.h
+++ b/refs.h
@@ -158,10 +158,14 @@ int dwim_log(const char *str, int len, struct object_id *oid, char **ref);
  * Retrieves the name of the main (or: primary) branch of the given
  * repository.
  *
+ * To obtain the default for newly-initialized repositories, pass the flag
+ * `MAIN_BRANCH_FOR_INIT`.
+ *
  * The result is an allocated string. Unless the flags ask for a short name, it
  * will be prefixed with "refs/heads/".
  */
 #define MAIN_BRANCH_FULL_NAME (1<<0)
+#define MAIN_BRANCH_FOR_INIT   (1<<1)
 char *git_main_branch_name(int flags);
 char *repo_main_branch_name(struct repository *r, int flags);
 
diff --git a/t/t0001-init.sh b/t/t0001-init.sh
index 5d8e321a703..fbf02066940 100755
--- a/t/t0001-init.sh
+++ b/t/t0001-init.sh
@@ -479,4 +479,20 @@ test_expect_success '--main-branch' '
 	grep hello actual
 '
 
+test_expect_success 'overridden default main branch name (config)' '
+	test_config_global init.defaultBranch nmb &&
+	git init main-branch-config &&
+	git -C main-branch-config symbolic-ref HEAD >actual &&
+	grep nmb actual &&
+	git -C main-branch-config config core.mainBranch >actual &&
+	echo nmb >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'invalid default branch name' '
+	test_config_global init.defaultBranch "with space" &&
+	test_must_fail git init main-branch-invalid 2>err &&
+	test_i18ngrep "invalid branch name" err
+'
+
 test_done
-- 
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