Merge branch 'rj/avoid-switching-to-already-used-branch'

A few subcommands have been taught to stop users from working on a
branch that is being used in another worktree linked to the same
repository.

* rj/avoid-switching-to-already-used-branch:
  switch: reject if the branch is already checked out elsewhere (test)
  rebase: refuse to switch to a branch already checked out elsewhere (test)
  branch: fix die_if_checked_out() when ignore_current_worktree
  worktree: introduce is_shared_symref()

2 files changed, 43 insertions, 0 deletions

diff --git a/t/t2060-switch.sh b/t/t2060-switch.sh
index 5a7caf958c..e247a4735b 100755
--- a/t/t2060-switch.sh
+++ b/t/t2060-switch.sh
@@ -146,4 +146,33 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'switch back when temporarily detached and checked out elsewhere ' '
+	test_when_finished "
+		git worktree remove wt1 ||:
+		git worktree remove wt2 ||:
+		git checkout - ||:
+		git branch -D shared ||:
+	" &&
+	git checkout -b shared &&
+	test_commit shared-first &&
+	HASH1=$(git rev-parse --verify HEAD) &&
+	test_commit shared-second &&
+	test_commit shared-third &&
+	HASH2=$(git rev-parse --verify HEAD) &&
+	git worktree add wt1 -f shared &&
+	git -C wt1 bisect start &&
+	git -C wt1 bisect good $HASH1 &&
+	git -C wt1 bisect bad $HASH2 &&
+	git worktree add wt2 -f shared &&
+	git -C wt2 bisect start &&
+	git -C wt2 bisect good $HASH1 &&
+	git -C wt2 bisect bad $HASH2 &&
+	# we test in both worktrees to ensure that works
+	# as expected with "first" and "next" worktrees
+	test_must_fail git -C wt1 switch shared &&
+	git -C wt1 switch --ignore-other-worktrees shared &&
+	test_must_fail git -C wt2 switch shared &&
+	git -C wt2 switch --ignore-other-worktrees shared
+'
+
 test_done
diff --git a/t/t3400-rebase.sh b/t/t3400-rebase.sh
index d5a8ee39fc..3ce918fdb8 100755
--- a/t/t3400-rebase.sh
+++ b/t/t3400-rebase.sh
@@ -388,6 +388,20 @@ test_expect_success 'switch to branch checked out here' '
 	git rebase main main
 '
 
+test_expect_success 'switch to branch checked out elsewhere fails' '
+	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_must_fail git -C wt1 rebase shared shared &&
+	test_must_fail git -C wt2 rebase shared shared
+'
+
 test_expect_success 'switch to branch not checked out' '
 	git checkout main &&
 	git branch other &&