Merge branch 'pw/3.0-default-initial-branch-to-main'

Declare that "git init" that is not otherwise configured uses
'main' as the initial branch, not 'master', starting Git 3.0.

* pw/3.0-default-initial-branch-to-main:
  t0613: stop setting default initial branch
  t9902: switch default branch name to main
  t4013: switch default branch name to main
  breaking-changes: switch default branch to main

Author: gitster

Documentation/BreakingChanges.adoc

@@ -165,6 +165,12 @@ A prerequisite for this change is that the ecosystem is ready to support the
 "reftable" format. Most importantly, alternative implementations of Git like
 JGit, libgit2 and Gitoxide need to support it.
 
+* In new repositories, the default branch name will be `main`. We have been
+  warning that the default name will change since 675704c74dd (init:
+  provide useful advice about init.defaultBranch, 2020-12-11).  The new name
+  matches the default branch name used in new repositories by many of the
+  big Git forges.
+
 === Removals
 
 * Support for grafting commits has long been superseded by git-replace(1).

Documentation/git-init.adoc

@@ -77,9 +77,15 @@ If this is a reinitialization, the repository will be moved to the specified pat
 `-b <branch-name>`::
 `--initial-branch=<branch-name>`::
 Use _<branch-name>_ for the initial branch in the newly created
-repository.  If not specified, fall back to the default name (currently
-`master`, but this is subject to change in the future; the name can be
-customized via the `init.defaultBranch` configuration variable).
+repository.  If not specified, fall back to the default name
+ifndef::with-breaking-changes[]
+(currently `master`, but this will change to `main` when Git 3.0 is released).
+endif::with-breaking-changes[]
+ifdef::with-breaking-changes[]
+`main`.
+endif::with-breaking-changes[]
+The default name can be customized via the `init.defaultBranch` configuration
+variable.
 
 `--shared[=(false|true|umask|group|all|world|everybody|<perm>)]`::
 

advice.c

@@ -51,7 +51,9 @@ static struct {
 	[ADVICE_AM_WORK_DIR] 				= { "amWorkDir" },
 	[ADVICE_CHECKOUT_AMBIGUOUS_REMOTE_BRANCH_NAME] 	= { "checkoutAmbiguousRemoteBranchName" },
 	[ADVICE_COMMIT_BEFORE_MERGE]			= { "commitBeforeMerge" },
+#ifndef WITH_BREAKING_CHANGES
 	[ADVICE_DEFAULT_BRANCH_NAME]			= { "defaultBranchName" },
+#endif /* WITH_BREAKING_CHANGES */
 	[ADVICE_DETACHED_HEAD]				= { "detachedHead" },
 	[ADVICE_DIVERGING]				= { "diverging" },
 	[ADVICE_FETCH_SET_HEAD_WARN]			= { "fetchRemoteHEADWarn" },

advice.h

@@ -18,7 +18,9 @@ enum advice_type {
 	ADVICE_AM_WORK_DIR,
 	ADVICE_CHECKOUT_AMBIGUOUS_REMOTE_BRANCH_NAME,
 	ADVICE_COMMIT_BEFORE_MERGE,
+#ifndef WITH_BREAKING_CHANGES
 	ADVICE_DEFAULT_BRANCH_NAME,
+#endif /* WITH_BREAKING_CHANGES */
 	ADVICE_DETACHED_HEAD,
 	ADVICE_DIVERGING,
 	ADVICE_FETCH_SET_HEAD_WARN,

ci/run-build-and-tests.sh

@@ -9,7 +9,6 @@ run_tests=t
 
 case "$jobname" in
 linux-breaking-changes)
-	export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 	export WITH_BREAKING_CHANGES=YesPlease
 	;;
 linux-TEST-vars)

refs.c

@@ -627,10 +627,12 @@ void expand_ref_prefix(struct strvec *prefixes, const char *prefix)
 		strvec_pushf(prefixes, *p, len, prefix);
 }
 
+#ifndef WITH_BREAKING_CHANGES
 static const char default_branch_name_advice[] = N_(
 "Using '%s' as the name for the initial branch. This default branch name\n"
-"is subject to change. To configure the initial branch name to use in all\n"
-"of your new repositories, which will suppress this warning, call:\n"
+"will change to \"main\" in Git 3.0. To configure the initial branch name\n"
+"to use in all of your new repositories, which will suppress this warning,\n"
+"call:\n"
 "\n"
 "\tgit config --global init.defaultBranch <name>\n"
 "\n"
@@ -639,8 +641,9 @@ static const char default_branch_name_advice[] = N_(
 "\n"
 "\tgit branch -m <name>\n"
 );
+#endif /* WITH_BREAKING_CHANGES */
 
-char *repo_default_branch_name(struct repository *r, int quiet)
+char *repo_default_branch_name(struct repository *r, MAYBE_UNUSED int quiet)
 {
 	const char *config_key = "init.defaultbranch";
 	const char *config_display_key = "init.defaultBranch";
@@ -649,14 +652,18 @@ char *repo_default_branch_name(struct repository *r, int quiet)
 
 	if (env && *env)
 		ret = xstrdup(env);
-	else if (repo_config_get_string(r, config_key, &ret) < 0)
+	if (!ret && repo_config_get_string(r, config_key, &ret) < 0)
 		die(_("could not retrieve `%s`"), config_display_key);
 
 	if (!ret) {
+#ifdef WITH_BREAKING_CHANGES
+		ret = xstrdup("main");
+#else
 		ret = xstrdup("master");
 		if (!quiet)
 			advise_if_enabled(ADVICE_DEFAULT_BRANCH_NAME,
 					  _(default_branch_name_advice), ret);
+#endif /* WITH_BREAKING_CHANGES */
 	}
 
 	full_ref = xstrfmt("refs/heads/%s", ret);

t/t0001-init.sh

@@ -868,7 +868,7 @@ test_expect_success 'overridden default initial branch name (config)' '
 	grep nmb actual
 '
 
-test_expect_success 'advice on unconfigured init.defaultBranch' '
+test_expect_success !WITH_BREAKING_CHANGES 'advice on unconfigured init.defaultBranch' '
 	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= git -c color.advice=always \
 		init unconfigured-default-branch-name 2>err &&
 	test_decode_color <err >decoded &&
@@ -883,6 +883,22 @@ test_expect_success 'advice on unconfigured init.defaultBranch disabled' '
 	test_grep ! "hint: " err
 '
 
+test_expect_success 'default branch name' '
+	if test_have_prereq WITH_BREAKING_CHANGES
+	then
+		expect=main
+	else
+		expect=master
+	fi &&
+	echo "refs/heads/$expect" >expect &&
+	(
+		sane_unset GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME &&
+		git init default-initial-branch-name
+	) &&
+	git -C default-initial-branch-name symbolic-ref HEAD >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'overridden default main branch name (env)' '
 	test_config_global init.defaultBranch nmb &&
 	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=env git init main-branch-env &&

t/t0613-reftable-write-options.sh

@@ -11,16 +11,18 @@ export GIT_TEST_REFTABLE_AUTOCOMPACTION
 # Block sizes depend on the hash function, so we force SHA1 here.
 GIT_TEST_DEFAULT_HASH=sha1
 export GIT_TEST_DEFAULT_HASH
-# Block sizes also depend on the actual refs we write, so we force "master" to
-# be the default initial branch name.
-GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master
-export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
 . ./test-lib.sh
 
+# Block sizes depend on the actual refs we write, so, for tests
+# that check block size, we force the initial branch name to be "master".
+init_repo () {
+	git init --initial-branch master repo
+}
+
 test_expect_success 'default write options' '
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -43,7 +45,7 @@ test_expect_success 'default write options' '
 test_expect_success 'disabled reflog writes no log blocks' '
 	test_config_global core.logAllRefUpdates false &&
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -62,7 +64,7 @@ test_expect_success 'disabled reflog writes no log blocks' '
 
 test_expect_success 'many refs results in multiple blocks' '
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -115,7 +117,7 @@ test_expect_success 'tiny block size leads to error' '
 test_expect_success 'small block size leads to multiple ref blocks' '
 	test_config_global core.logAllRefUpdates false &&
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit A &&
@@ -172,7 +174,7 @@ test_expect_success 'block size exceeding maximum supported size' '
 
 test_expect_success 'restart interval at every single record' '
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -212,7 +214,7 @@ test_expect_success 'restart interval exceeding maximum supported interval' '
 test_expect_success 'object index gets written by default with ref index' '
 	test_config_global core.logAllRefUpdates false &&
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&
@@ -247,7 +249,7 @@ test_expect_success 'object index gets written by default with ref index' '
 test_expect_success 'object index can be disabled' '
 	test_config_global core.logAllRefUpdates false &&
 	test_when_finished "rm -rf repo" &&
-	git init repo &&
+	init_repo &&
 	(
 		cd repo &&
 		test_commit initial &&