Re: [PATCH 6/6] breaking-changes: switch default branch to main

> diff --git a/Documentation/BreakingChanges.adoc b/Documentation/BreakingChanges.adoc
> index f8d2eba061c..93922299321 100644
> --- a/Documentation/BreakingChanges.adoc
> +++ b/Documentation/BreakingChanges.adoc
> @@ -165,6 +165,11 @@ 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.
>  
> +* 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 by many of the big git forges.
> +

> diff --git a/Documentation/git-init.adoc b/Documentation/git-init.adoc
> index a0dffba665f..39d4db6bccb 100644
> --- a/Documentation/git-init.adoc
> +++ b/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[]

> diff --git a/advice.c b/advice.c
> index e5f0ff84491..48c49ee4145 100644
> --- a/advice.c
> +++ b/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" },
> diff --git a/advice.h b/advice.h
> index 727dcecf4a3..fc1dc872049 100644
> --- a/advice.h
> +++ b/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,

> diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
> index 01823fd0f14..a21834043f3 100755
> --- a/ci/run-build-and-tests.sh
> +++ b/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

> diff --git a/refs.c b/refs.c
> index 4ff55cf24f6..e73f63ff6b8 100644
> --- a/refs.c
> +++ b/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"
> @@ -639,24 +641,32 @@ 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)
>  {
>  	const char *config_key = "init.defaultbranch";
>  	const char *config_display_key = "init.defaultBranch";
>  	char *ret = NULL, *full_ref;
> +#ifndef WITH_BREAKING_CHANGES
>  	const char *env = getenv("GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME");
>  
>  	if (env && *env)
>  		ret = xstrdup(env);
> -	else if (repo_config_get_string(r, config_key, &ret) < 0)
> +#endif /* WITH_BREAKING_CHANGES */

> +	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");
> +		(void) quiet; /* Silence -Wunused-parameter */
> +#else
>  		ret = xstrdup("master");
>  		if (!quiet)
>  			advise_if_enabled(ADVICE_DEFAULT_BRANCH_NAME,
>  					  _(default_branch_name_advice), ret);
> +#endif /* WITH_BREAKING_CHANGES */