Re: [PATCH v4] branch: add flags and config to inherit tracking

> I've addressed Glen's feedback from V3. However, this brings up a new
> issue that was not obvious before: "branch.<name>.merge" can be
> specified more than once. On the other hand, the existing tracking setup
> code supports only a single merge entry. For now I'm defaulting to use
> the first merge entry listed in the branch struct, but I'm curious what
> people think the best solution would be. This may be another point in
> favor of Ævar's suggestion to reuse the copy-branch-config machinery.

> +static int inherit_tracking(struct tracking *tracking, const char *orig_ref)
> +{
> +	const char *bare_ref;
> +	struct branch *branch;
> +
> +	bare_ref = orig_ref;
> +	skip_prefix(orig_ref, "refs/heads/", &bare_ref);
> +
> +	branch = branch_get(bare_ref);
> +	if (!branch->remote_name) {
> +		warning(_("asked to inherit tracking from %s, but no remote is set"),
> +			bare_ref);
> +		return -1;
> +	}
> +
> +	if (branch->merge_nr < 1 || !branch->merge_name || !branch->merge_name[0]) {
> +		warning(_("asked to inherit tracking from %s, but no merge configuration is set"),
> +			bare_ref);

> +		return -1;
> +	}
> +
> +	tracking->remote = xstrdup(branch->remote_name);
> +	tracking->src = xstrdup(branch->merge_name[0]);
> +	tracking->matches = 1;
> +	return 0;
> +}
> +
>  /*
>   * This is called when new_ref is branched off of orig_ref, and tries
>   * to infer the settings for branch.<new_ref>.{remote,merge} from the
> @@ -139,7 +166,9 @@ static void setup_tracking(const char *new_ref, const char *orig_ref,
>  
>  	memset(&tracking, 0, sizeof(tracking));
>  	tracking.spec.dst = (char *)orig_ref;
> -	if (for_each_remote(find_tracked_branch, &tracking))
> +	if (track != BRANCH_TRACK_INHERIT) {
> +		for_each_remote(find_tracked_branch, &tracking);
> +	} else if (inherit_tracking(&tracking, orig_ref))
>  		return;

> @@ -632,8 +632,10 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
>  		OPT__VERBOSE(&filter.verbose,
>  			N_("show hash and subject, give twice for upstream branch")),
>  		OPT__QUIET(&quiet, N_("suppress informational messages")),
> -		OPT_SET_INT('t', "track",  &track, N_("set up tracking mode (see git-pull(1))"),
> -			BRANCH_TRACK_EXPLICIT),
> +		OPT_CALLBACK_F('t', "track",  &track, "direct|inherit",
> +			N_("set up tracking mode (see git-pull(1))"),

> +			PARSE_OPT_OPTARG | PARSE_OPT_LITERAL_ARGHELP,
> +			parse_opt_tracking_mode),
>  		OPT_SET_INT_F(0, "set-upstream", &track, N_("do not use"),
>  			BRANCH_TRACK_OVERRIDE, PARSE_OPT_HIDDEN),
>  		OPT_STRING('u', "set-upstream-to", &new_upstream, N_("upstream"), N_("change the upstream info")),
> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index b5d477919a..45dab414ea 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -1532,8 +1532,10 @@ static struct option *add_common_switch_branch_options(
>  {
>  	struct option options[] = {
>  		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
> -		OPT_SET_INT('t', "track",  &opts->track, N_("set upstream info for new branch"),
> -			BRANCH_TRACK_EXPLICIT),
> +		OPT_CALLBACK_F('t', "track",  &opts->track, "direct|inherit",
> +			N_("set up tracking mode (see git-pull(1))"),
> +			PARSE_OPT_OPTARG | PARSE_OPT_LITERAL_ARGHELP,
> +			parse_opt_tracking_mode),
>  		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
>  			   PARSE_OPT_NOCOMPLETE),
>  		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
> diff --git a/config.c b/config.c
> index cb4a8058bf..4bd5a18faf 100644
> --- a/config.c
> +++ b/config.c
> @@ -1580,6 +1580,9 @@ static int git_default_branch_config(const char *var, const char *value)
>  		if (value && !strcasecmp(value, "always")) {
>  			git_branch_track = BRANCH_TRACK_ALWAYS;
>  			return 0;
> +		} else if (value && !strcasecmp(value, "inherit")) {
> +			git_branch_track = BRANCH_TRACK_INHERIT;
> +			return 0;
>  		}

> +test_expect_success 'checkout --track -b overrides autoSetupMerge=inherit' '
> +	# Set up tracking config on main
> +	git config branch.main.remote origin &&
> +	git config branch.main.merge refs/heads/main &&
> +	test_config branch.autoSetupMerge inherit &&
> +	# With --track=inherit, we copy the tracking config from main
> +	git checkout --track=inherit -b b1 main &&
> +	test_cmp_config origin branch.b1.remote &&
> +	test_cmp_config refs/heads/main branch.b1.merge &&
> +	# With branch.autoSetupMerge=inherit, we do the same
> +	git checkout -b b2 main &&
> +	test_cmp_config origin branch.b2.remote &&
> +	test_cmp_config refs/heads/main branch.b2.merge &&
> +	# But --track overrides this
> +	git checkout --track -b b3 main &&
> +	test_cmp_config . branch.b3.remote &&
> +	test_cmp_config refs/heads/main branch.b3.merge &&
> +	# And --track=direct does as well
> +	git checkout --track=direct -b b4 main &&
> +	test_cmp_config . branch.b4.remote &&
> +	test_cmp_config refs/heads/main branch.b4.merge
> +'
> +