t1409: check that `packed-refs` is not rewritten unnecessarily

There is no need to rewrite the `packed-refs` file except for the case
that we are deleting a reference that has a packed version. Verify
that `packed-refs` is not rewritten when it shouldn't be.

In fact, two of these tests fail:

* A new (empty) `packed-refs` file is created when deleting any loose
reference and no `packed-refs` file previously existed.

* The `packed-refs` file is rewritten unnecessarily when deleting a
loose reference that has no packed counterpart.

Both problems will be fixed in the next commit.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t1409-avoid-packing-refs.sh b/t/t1409-avoid-packing-refs.sh
new file mode 100755 (executable)
index 0000000..a2397c7
--- /dev/null
+++ b/t/t1409-avoid-packing-refs.sh
@@ -0,0 +1,118 @@
+#!/bin/sh
+
+test_description='avoid rewriting packed-refs unnecessarily'
+
+. ./test-lib.sh
+
+# Add an identifying mark to the packed-refs file header line. This
+# shouldn't upset readers, and it should be omitted if the file is
+# ever rewritten.
+mark_packed_refs () {
+       sed -e "s/^\(#.*\)/\1 t1409 /" <.git/packed-refs >.git/packed-refs.new &&
+       mv .git/packed-refs.new .git/packed-refs
+}
+
+# Verify that the packed-refs file is still marked.
+check_packed_refs_marked () {
+       grep -q '^#.* t1409 ' .git/packed-refs
+}
+
+test_expect_success 'setup' '
+       git commit --allow-empty -m "Commit A" &&
+       A=$(git rev-parse HEAD) &&
+       git commit --allow-empty -m "Commit B" &&
+       B=$(git rev-parse HEAD) &&
+       git commit --allow-empty -m "Commit C" &&
+       C=$(git rev-parse HEAD)
+'
+
+test_expect_failure 'do not create packed-refs file gratuitously' '
+       test_must_fail test -f .git/packed-refs &&
+       git update-ref refs/heads/foo $A &&
+       test_must_fail test -f .git/packed-refs &&
+       git update-ref refs/heads/foo $B &&
+       test_must_fail test -f .git/packed-refs &&
+       git update-ref refs/heads/foo $C $B &&
+       test_must_fail test -f .git/packed-refs &&
+       git update-ref -d refs/heads/foo &&
+       test_must_fail test -f .git/packed-refs
+'
+
+test_expect_success 'check that marking the packed-refs file works' '
+       git for-each-ref >expected &&
+       git pack-refs --all &&
+       mark_packed_refs &&
+       check_packed_refs_marked &&
+       git for-each-ref >actual &&
+       test_cmp expected actual &&
+       git pack-refs --all &&
+       test_must_fail check_packed_refs_marked &&
+       git for-each-ref >actual2 &&
+       test_cmp expected actual2
+'
+
+test_expect_success 'leave packed-refs untouched on update of packed' '
+       git update-ref refs/heads/packed-update $A &&
+       git pack-refs --all &&
+       mark_packed_refs &&
+       git update-ref refs/heads/packed-update $B &&
+       check_packed_refs_marked
+'
+
+test_expect_success 'leave packed-refs untouched on checked update of packed' '
+       git update-ref refs/heads/packed-checked-update $A &&
+       git pack-refs --all &&
+       mark_packed_refs &&
+       git update-ref refs/heads/packed-checked-update $B $A &&
+       check_packed_refs_marked
+'
+
+test_expect_success 'leave packed-refs untouched on verify of packed' '
+       git update-ref refs/heads/packed-verify $A &&
+       git pack-refs --all &&
+       mark_packed_refs &&
+       echo "verify refs/heads/packed-verify $A" | git update-ref --stdin &&
+       check_packed_refs_marked
+'
+
+test_expect_success 'touch packed-refs on delete of packed' '
+       git update-ref refs/heads/packed-delete $A &&
+       git pack-refs --all &&
+       mark_packed_refs &&
+       git update-ref -d refs/heads/packed-delete &&
+       test_must_fail check_packed_refs_marked
+'
+
+test_expect_success 'leave packed-refs untouched on update of loose' '
+       git pack-refs --all &&
+       git update-ref refs/heads/loose-update $A &&
+       mark_packed_refs &&
+       git update-ref refs/heads/loose-update $B &&
+       check_packed_refs_marked
+'
+
+test_expect_success 'leave packed-refs untouched on checked update of loose' '
+       git pack-refs --all &&
+       git update-ref refs/heads/loose-checked-update $A &&
+       mark_packed_refs &&
+       git update-ref refs/heads/loose-checked-update $B $A &&
+       check_packed_refs_marked
+'
+
+test_expect_success 'leave packed-refs untouched on verify of loose' '
+       git pack-refs --all &&
+       git update-ref refs/heads/loose-verify $A &&
+       mark_packed_refs &&
+       echo "verify refs/heads/loose-verify $A" | git update-ref --stdin &&
+       check_packed_refs_marked
+'
+
+test_expect_failure 'leave packed-refs untouched on delete of loose' '
+       git pack-refs --all &&
+       git update-ref refs/heads/loose-delete $A &&
+       mark_packed_refs &&
+       git update-ref -d refs/heads/loose-delete &&
+       check_packed_refs_marked
+'
+
+test_done