[PATCH 2/2] repack -ad: prune the list of shallow commits

From: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
Date: Jul 11, 2018, 22:23 UTC
Message-ID: <b4e01a963fd16f50d12c1f67c6e64bec8b1e9673.1531513093.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.9.git.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

While it is true that we never add unreachable commits into pack files intentionally (as `git repack`'s documentation states), we must not forget that a `git fetch --prune` (or even a `git fetch` when a ref was force-pushed in the meantime) can make a commit unreachable that was reachable before.

Therefore it is not safe to assume that a `git repack -adlf` will keep unreachable commits alone (under the assumption that they had not been packed in the first place).

This is particularly important to keep in mind when looking at the `.git/shallow` file: if any commits listed in that file become unreachable, it is not a problem, but if they go missing, it *is* a problem. One symptom of this problem is that a deepening fetch may now fail with

	fatal: error in object: unshallow <commit-hash>

To avoid this problem, let's prune the shallow list in `git repack` when the `-d` option is passed, unless `-A` is passed, too (which would force the now-unreachable objects to be turned into loose objects instead of being deleted).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 builtin/repack.c         | 4 ++++
 t/t5537-fetch-shallow.sh | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/builtin/repack.c b/builtin/repack.c
index 6c636e159..45f321b23 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -444,6 +444,10 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 		if (!quiet && isatty(2))
 			opts |= PRUNE_PACKED_VERBOSE;
 		prune_packed_objects(opts);
+
+		if (!(pack_everything & LOOSEN_UNREACHABLE) &&
+		    is_repository_shallow())
+			prune_shallow(0);
 	}
 
 	if (!no_update_server_info)
diff --git a/t/t5537-fetch-shallow.sh b/t/t5537-fetch-shallow.sh
index 561485d31..d32ba20f9 100755
--- a/t/t5537-fetch-shallow.sh
+++ b/t/t5537-fetch-shallow.sh
@@ -186,7 +186,7 @@ EOF
 	test_cmp expect actual
 '
 
-test_expect_failure '.git/shallow is edited by repack' '
+test_expect_success '.git/shallow is edited by repack' '
 	git init shallow-server &&
 	test_commit -C shallow-server A &&
 	test_commit -C shallow-server B &&

-- 
gitgitgadget