initial branch: give hints after switching the default name

It is likely that those who came to Git after 3.0 switched the
default initial branch name to 'main' would still try to follow
tutorials that were written before 3.0 happened and with the
assumption that the tool would call the initial branch 'master'.

To help these new users after 3.0 boundary, let's retain one part of
the hint we will be giving before the default changes, namely, how
to rename the branch an unconfigured Git has created just once.

We do this without telling them how to permanently configure the
default name of the initial branch, and that design choice is very
much deliberate.  The whole point of switching the default name was
because we did not want to force individual users to configure their
default branch name but while the hard wired default was 'master',
they _had_ to configure it away from 'master' in order to conform to
the recent norm, and a hint that tells them how to do so is useful.

But once the default is renamed to 'main', that no longer is true.
A narrower audience who are new users that follow an instruction
that assumes the initial branch name is 'master' would only need to
learn "here is how to change the branch name to match the tutorial
you are following in the repository you created for practice", and
"here is how you keep creating repositories with the first branch
with a name everybody hates" is unnecessary.

It also needs to be noted that the advise token to squelch the
message is the same advice.defaultBranchName as before, which is
also very much deliberate.  The users who do have that configured
are those who _have_ been using Git since before 3.0, and they are
not the target audience for the new advice message.  Reusing the
same advise token ensures that they do not have to turn the message
off.

Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

advice.c

@@ -51,9 +51,7 @@ 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

@@ -18,9 +18,7 @@ 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, /* To be retired sometime after Git 3.0 */
-	ADVICE_DEFAULT_BRANCH_NAME,
-#endif /* WITH_BREAKING_CHANGES */
 	ADVICE_DETACHED_HEAD,
 	ADVICE_DIVERGING,
 	ADVICE_FETCH_SET_HEAD_WARN,

refs.c

@@ -641,9 +641,17 @@ static const char default_branch_name_advice[] = N_(
 "\n"
 "\tgit branch -m <name>\n"
 );
+#else
+static const char default_branch_name_advice[] = N_(
+"Using '%s' as the name for the initial branch since Git 3.0.\n"
+"If you expected Git to create 'master', the just-created\n"
+"branch can be renamed via this command:\n"
+"\n"
+"\tgit branch -m master\n"
+);
 #endif /* WITH_BREAKING_CHANGES */
 
-char *repo_default_branch_name(struct repository *r, MAYBE_UNUSED int quiet)
+char *repo_default_branch_name(struct repository *r, int quiet)
 {
 	const char *config_key = "init.defaultbranch";
 	const char *config_display_key = "init.defaultBranch";
@@ -660,10 +668,10 @@ char *repo_default_branch_name(struct repository *r, MAYBE_UNUSED int quiet)
 		ret = xstrdup("main");
 #else
 		ret = xstrdup("master");
+#endif /* WITH_BREAKING_CHANGES */
 		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 !WITH_BREAKING_CHANGES 'advice on unconfigured init.defaultBranch' '
+test_expect_success '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 &&

t/test-lib.sh

@@ -127,13 +127,17 @@ then
 	export GIT_TEST_DISALLOW_ABBREVIATED_OPTIONS
 fi
 
+# Explicitly set the default branch name for testing, to squelch hints
+# from "git init" during the transition period.  Should be removed
+# after we decide to remove ADVICE_DEFAULT_BRANCH_NAME
 if test -z "$WITH_BREAKING_CHANGES"
 then
-	# Explicitly set the default branch name for testing, to avoid the
-	# transitory "git init" warning under --verbose.
 	: ${GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME:=master}
-	export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+else
+	: ${GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME:=main}
 fi
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
 
 ################################################################
 # It appears that people try to run tests without building...