Re: [PATCH v2 02/12] fmt-merge-msg: introduce a way to override the main branch name

> On 15/06/2020 13:50, Johannes Schindelin via GitGitGadget wrote:
> > From: Johannes Schindelin <johannes.schindelin@gmx.de>
> >
> > There is a growing number of projects and companies desiring to change
> > the main branch name of their repositories (see e.g.
> > https://twitter.com/mislav/status/1270388510684598272 for background on
> > this).
>
> I think this is a good way of phrasing the rationale for the change

> > However, there are a couple of hard-coded spots in Git's source code
> > that make this endeavor harder than necessary. For example, when
> > formatting the commit message for merge commits, Git appends "into
> > <branch-name>" unless the current branch is the `master` branch.
> >
> > Clearly, this is not what one wants when already having gone through all
> > the steps to manually rename the main branch
>
> This didn't quite scan for me maybe s/already having/one has already/ ?

> > (and taking care of all the
> > fall-out such as re-targeting existing Pull Requests).
> >
> > Let's introduce a way to override Git's hard-coded default:
> > `core.mainBranch`.
> >
> > We will start supporting this config option in the `git fmt-merge-msg`
> > command and successively adjust all other places where the main branch
> > name is hard-coded.
> >
> > Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> > ---
> >   Documentation/config/core.txt |  5 +++++
> >   fmt-merge-msg.c               |  6 ++++--
> >   refs.c                        | 27 +++++++++++++++++++++++++++
> >   refs.h                        |  7 +++++++
> >   t/t6200-fmt-merge-msg.sh      |  7 +++++++
> >   5 files changed, 50 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt
> > index 74619a9c03b..32bb5368ebb 100644
> > --- a/Documentation/config/core.txt
> > +++ b/Documentation/config/core.txt
> > @@ -626,3 +626,8 @@ core.abbrev::
> >    in your repository, which hopefully is enough for
> >    abbreviated object names to stay unique for some time.
> >    The minimum length is 4.
> > +
> > +core.mainBranch::
> > +	The name of the main (or: primary) branch in the current repository.
> > +	For historical reasons, `master` is used as the fall-back for this
> > +	setting.
> > diff --git a/fmt-merge-msg.c b/fmt-merge-msg.c
> > index 72d32bd73b1..43f4f829242 100644
> > --- a/fmt-merge-msg.c
> > +++ b/fmt-merge-msg.c
> > @@ -407,7 +407,7 @@ static void fmt_merge_msg_title(struct strbuf *out,
> >   				const char *current_branch)
> >   {
> >   	int i = 0;
> > -	char *sep = "";
> > +	char *sep = "", *main_branch;
> >
> >    strbuf_addstr(out, "Merge ");
> >    for (i = 0; i < srcs.nr; i++) {
> > @@ -451,10 +451,12 @@ static void fmt_merge_msg_title(struct strbuf *out,
> >    		strbuf_addf(out, " of %s", srcs.items[i].string);
> >    }
> >   -	if (!strcmp("master", current_branch))
> > +	main_branch = git_main_branch_name();
> > +	if (!strcmp(main_branch, current_branch))
> >    	strbuf_addch(out, '\n');
> >    else
> >   		strbuf_addf(out, " into %s\n", current_branch);
> > +	free(main_branch);
> >   }
> >
> >   static void fmt_tag_signature(struct strbuf *tagbuf,
> > diff --git a/refs.c b/refs.c
> > index 224ff66c7bb..f1854cffa2f 100644
> > --- a/refs.c
> > +++ b/refs.c
> > @@ -560,6 +560,33 @@ void expand_ref_prefix(struct argv_array *prefixes,
> > const char *prefix)
> >   		argv_array_pushf(prefixes, *p, len, prefix);
> >   }
> >
> > +char *repo_main_branch_name(struct repository *r)
> > +{
> > +	const char *config_key = "core.mainbranch";
> > +	const char *config_display_key = "core.mainBranch";
> > +	const char *fall_back = "master";
> > +	char *name = NULL, *ret;
> > +
> > +	if (repo_config_get_string(r, config_key, &name) < 0)
> > +		die(_("could not retrieve `%s`"), config_display_key);
> > +
> > +	ret = name ? name : xstrdup(fall_back);
> > +
> > +	if (check_refname_format(ret, REFNAME_ALLOW_ONELEVEL))
> > +		die(_("invalid branch name: %s = %s"),
> > +		    config_display_key, name);
> > +
> > +	if (name != ret)
> > +		free(name);
>
> I'm struggling to come up with a scenario where name != NULL && name != ret
> here, however once we get to patch 4 that scenario definitely does exist.

>
> > +
> > +	return ret;
> > +}
> > +
> > +char *git_main_branch_name(void)
> > +{
> > +	return repo_main_branch_name(the_repository);
> > +}
> > +
> >   /*
> >    * *string and *len will only be substituted, and *string returned (for
> >    * later free()ing) if the string passed in is a magic short-hand form
> > diff --git a/refs.h b/refs.h
> > index a92d2c74c83..a207ef01348 100644
> > --- a/refs.h
> > +++ b/refs.h
> > @@ -154,6 +154,13 @@ int repo_dwim_log(struct repository *r, const char
> > *str, int len, struct object_
> >   int dwim_ref(const char *str, int len, struct object_id *oid, char **ref);
> >   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
>
> nit pick, I'm confused by the ':'

>
> Best Wishes
>
> Phillip
>
> > + * repository.
> > + */
> > +char *git_main_branch_name(void);
> > +char *repo_main_branch_name(struct repository *r);
> > +
> >   /*
> >    * A ref_transaction represents a collection of reference updates that
> >    * should succeed or fail together.
> > diff --git a/t/t6200-fmt-merge-msg.sh b/t/t6200-fmt-merge-msg.sh
> > index e4c2a6eca43..7a873f4a05c 100755
> > --- a/t/t6200-fmt-merge-msg.sh
> > +++ b/t/t6200-fmt-merge-msg.sh
> > @@ -158,6 +158,13 @@ test_expect_success 'setup FETCH_HEAD' '
> >   	git fetch . left
> >   '
> >
> > +test_expect_success 'with overridden default branch name' '
> > +	test_when_finished "git switch master" &&
> > +	git switch -c default &&
> > +	git -c core.mainBranch=default fmt-merge-msg <.git/FETCH_HEAD >actual
> > &&
> > +	! grep "into default" actual
> > +'
> > +
> >   test_expect_success 'merge.log=3 limits shortlog length' '
> >    cat >expected <<-EOF &&
> >    Merge branch ${apos}left${apos}
> >
>
>