Under certain circumstances, commits that were reachable can be made unreachable, e.g. via git fetch --prune. These commits might have been packed already, in which case git repack -adlf will just drop them without giving them the usual grace period before an eventual git prune (via git gc) prunes them. This is a problem when the shallow file still lists them, which is the reason why git prune edits that file. And with the proposed changes, git repack -ad will now do the same. Reported by Alejandro Pauly. Changes since v2: * Fixed a typo in the last commit message. * Added an explanation to the last commit message why we do not simply skip non-existing shallow commits at fetch time. * Introduced a new, "quick prune" mode where prune_shallow() does not try to drop unreachable commits, but only non-existing ones. * Rebased to current master because there were too many merge conflicts for my liking otherwise. Changes since v1: * Also trigger prune_shallow() when --unpack-unreachable=<approxidate> was passed to git repack. * No need to trigger prune_shallow() when git repack was called with -k. Johannes Schindelin (3): repack: point out a bug handling stale shallow info shallow: offer to prune only non-existing entries repack -ad: prune the list of shallow commits builtin/prune.c | 2 +- builtin/repack.c | 6 ++++++ commit.h | 2 +- shallow.c | 22 +++++++++++++++++----- t/t5537-fetch-shallow.sh | 27 +++++++++++++++++++++++++++ 5 files changed, 52 insertions(+), 7 deletions(-) base-commit: c4df23f7927d8d00e666a3c8d1b3375f1dc8a3c1 Published-As: https://github.com/gitgitgadget/git/releases/tags/pr-9%2Fdscho%2Fshallow-and-fetch-prune-v3 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-9/dscho/shallow-and-fetch-prune-v3 Pull-Request: https://github.com/gitgitgadget/git/pull/9 Range-diff vs v2: 1: d2be40131 ! 1: ed8559b91 repack: point out a bug handling stale shallow info @@ -48,4 +48,6 @@ + origin "+refs/heads/*:refs/remotes/origin/*" +' + - test_done + . "$TEST_DIRECTORY"/lib-httpd.sh + start_httpd + -: --------- > 2: f085eb4f7 shallow: offer to prune only non-existing entries 2: c7ee6e008 ! 3: 1f9ff57d5 repack -ad: prune the list of shallow commits @@ -2,15 +2,19 @@ repack -ad: prune the list of shallow commits - 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 + `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). + 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 @@ -23,8 +27,16 @@ 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, e also need to take `--keep-reachable` and - `--unpack-unreachable=<date>` into account. + being deleted). Additionally, we also need to take `--keep-reachable` + and `--unpack-unreachable=<date>` 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 <johannes.schindelin@xxxxxx> @@ -32,15 +44,15 @@ --- a/builtin/repack.c +++ b/builtin/repack.c @@ - if (!quiet && isatty(2)) + if (!po_args.quiet && isatty(2)) opts |= PRUNE_PACKED_VERBOSE; prune_packed_objects(opts); + + if (!keep_unreachable && + (!(pack_everything & LOOSEN_UNREACHABLE) || + unpack_unreachable) && -+ is_repository_shallow()) -+ prune_shallow(0); ++ is_repository_shallow(the_repository)) ++ prune_shallow(0, 1); } if (!no_update_server_info) -- gitgitgadget
