bisect: fix "reset" when branch is checked out elsewhere

Since 1d0fa89 (checkout: add --ignore-other-wortrees, 2015-01-03) we
have a safety valve in checkout/switch to prevent the same branch from
being checked out simultaneously in multiple worktrees.

If a branch is bisected in a worktree while also being checked out in
another worktree; when the bisection is finished, checking out the
branch back in the current worktree may fail.

Let's teach bisect to use the "--ignore-other-worktrees" flag.

Signed-off-by: Rubén Justo <rjusto@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/bisect.c

@@ -244,7 +244,8 @@ static int bisect_reset(const char *commit)
 		struct child_process cmd = CHILD_PROCESS_INIT;
 
 		cmd.git_cmd = 1;
-		strvec_pushl(&cmd.args, "checkout", branch.buf, "--", NULL);
+		strvec_pushl(&cmd.args, "checkout", "--ignore-other-worktrees",
+				branch.buf, "--", NULL);
 		if (run_command(&cmd)) {
 			error(_("could not check out original"
 				" HEAD '%s'. Try 'git bisect"

t/t6030-bisect-porcelain.sh

@@ -122,6 +122,29 @@ test_expect_success 'bisect start without -- takes unknown arg as pathspec' '
 	grep bar ".git/BISECT_NAMES"
 '
 
+test_expect_success 'bisect reset: back in a branch checked out also elsewhere' '
+	echo "shared" > branch.expect &&
+	test_bisect_reset() {
+		git -C $1 bisect start &&
+		git -C $1 bisect good $HASH1 &&
+		git -C $1 bisect bad $HASH3 &&
+		git -C $1 bisect reset &&
+		git -C $1 branch --show-current > branch.output &&
+		cmp branch.expect branch.output
+	} &&
+	test_when_finished "
+		git worktree remove wt1 &&
+		git worktree remove wt2 &&
+		git branch -d shared
+	" &&
+	git worktree add wt1 -b shared &&
+	git worktree add wt2 -f shared &&
+	# we test in both worktrees to ensure that works
+	# as expected with "first" and "next" worktrees
+	test_bisect_reset wt1 &&
+	test_bisect_reset wt2
+'
+
 test_expect_success 'bisect reset: back in the main branch' '
 	git bisect reset &&
 	echo "* main" > branch.expect &&