From 328a43518244b970e1765eca78060bfeb265a584 Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Wed, 24 Oct 2018 08:56:10 -0700 Subject: repack: point out a bug handling stale shallow info A `git fetch --prune` can turn previously-reachable objects unreachable, even commits that are in the `shallow` list. A subsequent `git repack -ad` will then unceremoniously drop those unreachable commits, and the `shallow` list will become stale. This means that when we try to fetch with a larger `--depth` the next time, we may end up with: fatal: error in object: unshallow Reported by Alejandro Pauly. Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- t/t5537-fetch-shallow.sh | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) (limited to 't') diff --git a/t/t5537-fetch-shallow.sh b/t/t5537-fetch-shallow.sh index 7045685e2d..686fdc9280 100755 --- a/t/t5537-fetch-shallow.sh +++ b/t/t5537-fetch-shallow.sh @@ -186,6 +186,33 @@ EOF test_cmp expect actual ' +test_expect_failure '.git/shallow is edited by repack' ' + git init shallow-server && + test_commit -C shallow-server A && + test_commit -C shallow-server B && + git -C shallow-server checkout -b branch && + test_commit -C shallow-server C && + test_commit -C shallow-server E && + test_commit -C shallow-server D && + d="$(git -C shallow-server rev-parse --verify D^0)" && + git -C shallow-server checkout master && + + git clone --depth=1 --no-tags --no-single-branch \ + "file://$PWD/shallow-server" shallow-client && + + : now remove the branch and fetch with prune && + git -C shallow-server branch -D branch && + git -C shallow-client fetch --prune --depth=1 \ + origin "+refs/heads/*:refs/remotes/origin/*" && + git -C shallow-client repack -adfl && + test_must_fail git -C shallow-client rev-parse --verify $d^0 && + ! grep $d shallow-client/.git/shallow && + + git -C shallow-server branch branch-orig $d && + git -C shallow-client fetch --prune --depth=2 \ + origin "+refs/heads/*:refs/remotes/origin/*" +' + . "$TEST_DIRECTORY"/lib-httpd.sh start_httpd -- cgit v1.2.3 From 5dcfbf564c0f10869e568af4e05421f63b44fbbf Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Wed, 24 Oct 2018 08:56:13 -0700 Subject: repack -ad: prune the list of shallow commits `git repack` can drop unreachable commits without further warning, making the corresponding entries in `.git/shallow` invalid, which causes serious problems when deepening the branches. One scenario where unreachable commits are dropped by `git repack` is when 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, which is an assumption at least some of Git's code seems to make). 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 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). Additionally, we also need to take `--keep-reachable` and `--unpack-unreachable=` into account. Note: an alternative solution discussed during the review of this patch was to teach `git fetch` to simply ignore entries in .git/shallow if the corresponding commits do not exist locally. A quick test, however, revealed that the .git/shallow file is written during a shallow *clone*, in which case the commits do not exist, either, but the "shallow" line *does* need to be sent. Therefore, this approach would be a lot more finicky than the approach presented by the this patch. Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- t/t5537-fetch-shallow.sh | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 't') diff --git a/t/t5537-fetch-shallow.sh b/t/t5537-fetch-shallow.sh index 686fdc9280..6faf17e17a 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 && -- cgit v1.2.3