Re: [PATCH v3] branch: show rebase/bisect info when possible instead of "(no branch)"

[Junio C Hamano <gitster@pobox.com>]

Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:

> This prints more helpful info when HEAD is detached: is it detached
> because of bisect or rebase? What is the original branch name in those
> cases?
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  Keep "no branch" in all cases. Just append "rebasing/bisecting [%s]"
>  when applicable.
>
>  builtin/branch.c            | 44 +++++++++++++++++++++++++++++++++++++++++++-
>  t/t6030-bisect-porcelain.sh |  2 +-
>  2 files changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/branch.c b/builtin/branch.c
> index 6371bf9..26c0c3d 100644
> --- a/builtin/branch.c
> +++ b/builtin/branch.c
> @@ -550,6 +550,48 @@ static int calc_maxwidth(struct ref_list *refs)
>  	return w;
>  }
>  
> +static char *get_head_description()
> +{
> +	struct stat st;
> +	struct strbuf sb = STRBUF_INIT;
> +	struct strbuf result = STRBUF_INIT;
> +	int bisect = 0;
> +	int ret;
> +	if (!stat(git_path("rebase-merge"), &st) && S_ISDIR(st.st_mode))
> +		ret = strbuf_read_file(&sb, git_path("rebase-merge/head-name"), 0);
> +	else if (!access(git_path("rebase-apply/rebasing"), F_OK))
> +		ret = strbuf_read_file(&sb, git_path("rebase-apply/head-name"), 0);
> +	else if (!access(git_path("BISECT_LOG"), F_OK)) {
> +		ret = strbuf_read_file(&sb, git_path("BISECT_START"), 0);
> +		bisect = 1;
> +	} else
> +		return xstrdup(_("(no branch)"));
> +
> +	if (ret <= 0) {

Doesn't the general "negative signals an error" apply here?

The end result may be the same, as the later part of this function
that uses sb with len==0 ends up showing the same "bisecting" (or
"rebasing") without any other information, but the logic to reach
that outcome looks wrong.

> +		if (bisect)
> +			return xstrdup(_("(no branch, bisecting)"));
> +		else
> +			return xstrdup(_("_(no branch, rebasing)"));
> +	}
> +
> +	while (sb.len && sb.buf[sb.len - 1] == '\n')
> +		strbuf_setlen(&sb, sb.len - 1);
> +
> +	if (bisect) {
> +		unsigned char sha1[20];
> +		if (!get_sha1_hex(sb.buf, sha1))
> +			strbuf_addstr(&result, _("(no branch, bisecting)"));
> +		else
> +			strbuf_addf(&result, _("(no branch, bisecting %s)"), sb.buf);
> +	} else {
> +		if (!prefixcmp(sb.buf, "refs/heads/"))
> +			strbuf_addf(&result, _("(no branch, rebasing %s)"), sb.buf + 11);
> +		else
> +			strbuf_addstr(&result, _("(no branch, rebasing)"));
> +	}
> +	strbuf_release(&sb);
> +	return strbuf_detach(&result, NULL);
> +}

We may want to refactor wt_status_print_state() and its callee a bit
so that it and this part can share the logic without duplication and
risk implementing subtly different decision.  wt_status used to have
clean separation between collection phase and presentation phase,
but the wall between the phases seems deteriorated over time as more
"in progress" crufts have been piled on top.

Such a refactoring may look larger than necessary, but on the other
hand, I do not see this feature very useful if it can over time
drift away from what we will see in "git status", so...

>  
>  static void show_detached(struct ref_list *ref_list)
>  {
> @@ -557,7 +599,7 @@ static void show_detached(struct ref_list *ref_list)
>  
>  	if (head_commit && is_descendant_of(head_commit, ref_list->with_commit)) {
>  		struct ref_item item;
> -		item.name = xstrdup(_("(no branch)"));
> +		item.name = get_head_description();
>  		item.width = utf8_strwidth(item.name);
>  		item.kind = REF_LOCAL_BRANCH;
>  		item.dest = NULL;
> diff --git a/t/t6030-bisect-porcelain.sh b/t/t6030-bisect-porcelain.sh
> index 3e0e15f..9b6f0d0 100755
> --- a/t/t6030-bisect-porcelain.sh
> +++ b/t/t6030-bisect-porcelain.sh
> @@ -164,7 +164,7 @@ test_expect_success 'bisect start: existing ".git/BISECT_START" not modified if
>  	cp .git/BISECT_START saved &&
>  	test_must_fail git bisect start $HASH4 foo -- &&
>  	git branch > branch.output &&
> -	test_i18ngrep "* (no branch)" branch.output > /dev/null &&
> +	test_i18ngrep "* (no branch, bisecting other)" branch.output > /dev/null &&
>  	test_cmp saved .git/BISECT_START
>  '
>  test_expect_success 'bisect start: no ".git/BISECT_START" if mistaken rev' '