Re: [PATCH] bisect: don't use invalid oid as rev when starting

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Christian,

On Wed, 23 Sep 2020, Johannes Schindelin wrote:

> On Wed, 23 Sep 2020, Christian Couder wrote:
>
> > diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
> > index 7dcc1b5188..538fa6f16b 100644
> > --- a/builtin/bisect--helper.c
> > +++ b/builtin/bisect--helper.c
> > @@ -486,12 +486,16 @@ static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
> >  			return error(_("unrecognized option: '%s'"), arg);
> >  		} else {
> >  			char *commit_id = xstrfmt("%s^{commit}", arg);
> > -			if (get_oid(commit_id, &oid) && has_double_dash)
> > -				die(_("'%s' does not appear to be a valid "
> > -				      "revision"), arg);
> > -
> > -			string_list_append(&revs, oid_to_hex(&oid));
> > +			int res = get_oid(commit_id, &oid);
> >  			free(commit_id);
> > +			if (res) {
> > +				if (has_double_dash)
> > +					die(_("'%s' does not appear to be a valid "
> > +					      "revision"), arg);
> > +				break;
> > +			} else {
> > +				string_list_append(&revs, oid_to_hex(&oid));
> > +			}
>
> I would find that a lot easier to read if it was reordered thusly:
>
> 			if (!get_oidf(&oid, "%s^{commit}", arg))
> 				string_list_append(&revs, oid_to_hex(&oid));
> 			else if (!has_double_dash)
> 				break;
> 			else
> 				die(_("'%s' does not appear to be a valid "
> 				      revision"), arg);
>
> And it would actually probably make sense to replace the `get_oid()` by
> `get_oid_committish()` in the first place.

I verified that this actually works, and figured out that we can save yet
another indentation level (as well as avoid awfully long lines):

-- snipsnap --
From f673cea53e046774847be918f4023430e56bf6cb Mon Sep 17 00:00:00 2001
From: Christian Couder <christian.couder@gmail.com>
Date: Wed, 23 Sep 2020 19:09:15 +0200
Subject: [PATCH] bisect: don't use invalid oid as rev when starting

In 06f5608c14 (bisect--helper: `bisect_start` shell function
partially in C, 2019-01-02), we changed the following shell
code:

	rev=$(git rev-parse -q --verify "$arg^{commit}") || {
		test $has_double_dash -eq 1 &&
		die "$(eval_gettext "'\$arg' does not appear to be a valid revision")"
		break
	}
	revs="$revs $rev"

into:

	char *commit_id = xstrfmt("%s^{commit}", arg);
	if (get_oid(commit_id, &oid) && has_double_dash)
		die(_("'%s' does not appear to be a valid "
		      "revision"), arg);

	string_list_append(&revs, oid_to_hex(&oid));
	free(commit_id);

In case of an invalid "arg" when "has_double_dash" is false, the old
code would "break" out of the argument loop.

In the new C code though, `oid_to_hex(&oid)` is unconditonally
appended to "revs". This is wrong first because "oid" is junk as
`get_oid(commit_id, &oid)` failed and second because it doesn't break
out of the argument loop.

Not breaking out of the argument loop means that "arg" is then not
treated as a path restriction (which is wrong).

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 builtin/bisect--helper.c    | 17 ++++++-----------
 t/t6030-bisect-porcelain.sh |  7 +++++++
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
index 93e855271b9..d11d4c9bbb5 100644
--- a/builtin/bisect--helper.c
+++ b/builtin/bisect--helper.c
@@ -660,18 +660,13 @@ static enum bisect_error bisect_start(struct bisect_terms *terms, const char **a
 			terms->term_bad = xstrdup(arg);
 		} else if (starts_with(arg, "--")) {
 			return error(_("unrecognized option: '%s'"), arg);
-		} else {
-			char *commit_id = xstrfmt("%s^{commit}", arg);
-			if (get_oid(commit_id, &oid) && has_double_dash) {
-				error(_("'%s' does not appear to be a valid "
-					"revision"), arg);
-				free(commit_id);
-				return BISECT_FAILED;
-			}
-
+		} else if (!get_oid_committish(arg, &oid))
 			string_list_append(&revs, oid_to_hex(&oid));
-			free(commit_id);
-		}
+		else if (has_double_dash)
+			die(_("'%s' does not appear to be a valid "
+			      "revision"), arg);
+		else
+			break;
 	}
 	pathspec_pos = i;

diff --git a/t/t6030-bisect-porcelain.sh b/t/t6030-bisect-porcelain.sh
index b886529e596..d6b4bca482a 100755
--- a/t/t6030-bisect-porcelain.sh
+++ b/t/t6030-bisect-porcelain.sh
@@ -82,6 +82,13 @@ test_expect_success 'bisect fails if given any junk instead of revs' '
 	git bisect bad $HASH4
 '

+test_expect_success 'bisect start without -- uses unknown arg as pathspec' '
+	git bisect reset &&
+	git bisect start foo bar &&
+	grep foo ".git/BISECT_NAMES" &&
+	grep bar ".git/BISECT_NAMES"
+'
+
 test_expect_success 'bisect reset: back in the master branch' '
 	git bisect reset &&
 	echo "* master" > branch.expect &&
--
2.28.0.windows.1.18.g5300e52e185