From beb6f24beef67f6f825c8c99e408f67d23b784d4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nguy=E1=BB=85n=20Th=C3=A1i=20Ng=E1=BB=8Dc=20Duy?=
 <pclouds@gmail.com>
Date: Mon, 15 Feb 2016 20:35:33 +0700
Subject: [PATCH] worktree add -B: do the checkout test before update branch
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

If --force is not given but -B is, we should not proceed if the given
branch is already checked out elsewhere. add_worktree() has this test,
but it kicks in too late when "git branch --force" is already
executed. As a result, even though we correctly refuse to create a new
worktree, we have already updated the branch and mess up the other
checkout.

Repeat the die_if_checked_out() test again for this specific case before
"git branch" runs.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/worktree.c      | 11 ++++++++++-
 t/t2025-worktree-add.sh |  7 +++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/builtin/worktree.c b/builtin/worktree.c
index 6b9c946693..20cf67a549 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -334,9 +334,18 @@ static int add(int ac, const char **av, const char *prefix)
 	branch = ac < 2 ? "HEAD" : av[1];
 
 	opts.force_new_branch = !!new_branch_force;
-	if (opts.force_new_branch)
+	if (opts.force_new_branch) {
+		struct strbuf symref = STRBUF_INIT;
+
 		opts.new_branch = new_branch_force;
 
+		if (!opts.force &&
+		    !strbuf_check_branch_ref(&symref, opts.new_branch) &&
+		    ref_exists(symref.buf))
+			die_if_checked_out(symref.buf);
+		strbuf_release(&symref);
+	}
+
 	if (ac < 2 && !opts.new_branch && !opts.detach) {
 		int n;
 		const char *s = worktree_basename(path, &n);
diff --git a/t/t2025-worktree-add.sh b/t/t2025-worktree-add.sh
index a4d36c0892..cbfa41ec61 100755
--- a/t/t2025-worktree-add.sh
+++ b/t/t2025-worktree-add.sh
@@ -193,6 +193,13 @@ test_expect_success '"add" -B/--detach mutually exclusive' '
 	test_must_fail git worktree add -B poodle --detach bamboo master
 '
 
+test_expect_success '"add -B" fails if the branch is checked out' '
+	git rev-parse newmaster >before &&
+	test_must_fail git worktree add -B newmaster bamboo master &&
+	git rev-parse newmaster >after &&
+	test_cmp before after
+'
+
 test_expect_success 'add -B' '
 	git worktree add -B poodle bamboo2 master^ &&
 	git -C bamboo2 symbolic-ref HEAD >actual &&