Add a place for (not) sharing stuff between worktrees

When multiple worktrees are used, we need rules to determine if
something belongs to one worktree or all of them. Instead of keeping
adding rules when new stuff comes (*), have a generic rule:

- Inside $GIT_DIR, which is per-worktree by default, add
  $GIT_DIR/common which is always shared. New features that want to
  share stuff should put stuff under this directory.

- Inside refs/, which is shared by default except refs/bisect, add
  refs/worktree/ which is per-worktree. We may eventually move
  refs/bisect to this new location and remove the exception in refs
  code.

(*) And it may also include stuff from external commands which will
    have no way to modify common/per-worktree rules.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 35 insertions, 0 deletions

diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index cd74c0a..c7b53e4 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -306,6 +306,8 @@ test_git_path GIT_COMMON_DIR=bar hooks/me                 bar/hooks/me
 test_git_path GIT_COMMON_DIR=bar config                   bar/config
 test_git_path GIT_COMMON_DIR=bar packed-refs              bar/packed-refs
 test_git_path GIT_COMMON_DIR=bar shallow                  bar/shallow
+test_git_path GIT_COMMON_DIR=bar common                   bar/common
+test_git_path GIT_COMMON_DIR=bar common/file              bar/common/file
 
 # In the tests below, $(pwd) must be used because it is a native path on
 # Windows and avoids MSYS's path mangling (which simplifies "foo/../bar" and
diff --git a/t/t1415-worktree-refs.sh b/t/t1415-worktree-refs.sh
new file mode 100755
index 0000000..16c91be
--- /dev/null
+++ b/t/t1415-worktree-refs.sh
@@ -0,0 +1,33 @@
+#!/bin/sh
+
+test_description='per-worktree refs'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit initial &&
+	test_commit wt1 &&
+	test_commit wt2 &&
+	git worktree add wt1 wt1 &&
+	git worktree add wt2 wt2 &&
+	git checkout initial &&
+	git update-ref refs/worktree/foo HEAD &&
+	git -C wt1 update-ref refs/worktree/foo HEAD &&
+	git -C wt2 update-ref refs/worktree/foo HEAD
+'
+
+test_expect_success 'refs/worktree must not be packed' '
+	git pack-refs --all &&
+	test_path_is_missing .git/refs/tags/wt1 &&
+	test_path_is_file .git/refs/worktree/foo &&
+	test_path_is_file .git/worktrees/wt1/refs/worktree/foo &&
+	test_path_is_file .git/worktrees/wt2/refs/worktree/foo
+'
+
+test_expect_success 'refs/worktree are per-worktree' '
+	test_cmp_rev worktree/foo initial &&
+	( cd wt1 && test_cmp_rev worktree/foo wt1 ) &&
+	( cd wt2 && test_cmp_rev worktree/foo wt2 )
+'
+
+test_done