[PATCH v3] filter-branch: fix commit map init from state branch
- From
- Grant Moyer <dev@grantmoyer.com>
- Date
- Oct 3, 2026, 01:01 UTC
- Message-ID
- <20261003010128.256757-1-dev@grantmoyer.com>
- In-Reply-To
- <20261001012347.3998801-1-dev@grantmoyer.com>
The "--state-branch" option asks git-filter-branch(1) to write a mapping from old to new objects into a branch to enable incremental processing of large histories. This object mapping is stored as a simple blob at "$state_branch:filter.map" with one object pair per line in the format "$from_commit:$to_commit". Before processing commits in a subsequent run, the state branch is used to populate an object mapping directory, where each file is named "map/$from_commit" and has contents "$to_commit".
In f6d855091e (filter-branch: stop depending on Perl, 2025-04-16), we refactored git-filter-branch(1) to no longer require Perl, but accidentally started to interpret object pairs in reverse (as "$to_commit:$from_commit") when populating the map directory from the state branch. This can cause all kinds of bad behavior from the state-branch being effectively ignored to previously filtered objects accidentally being mapped back to unfiltered objects. One especially evident case occurs when "git filter-branch --prune-empty ..." maps some commits to nothing, then on subsequent runs outputs many errors while trying to create files with empty names, like:
> /usr/lib/git-core/git-filter-branch: line 305: ../map/: Is a directory
This regression went unnoticed because, since the introduction of the only test for "--state-branch" in 709cfe848a (filter-branch: skip commits present on --state-branch, 2018-06-26), the test accidentally passes even if commits are not skipped. The test checks that after populating a state branch with git-filter-branch(1), then running it again with that state branch, the resulting filtered commits for the first run and second run match. However since the filter used is deterministic, the commits always match, even if the commits in the state branch are re-filtered.
Fix the population of the object mapping dir by interpreting object pairs as "$from_commit:$to_commit". Also fix the existing "--state-branch" test by directly exiting with a non-zero code if any commits from the state branch aren't skipped. Finally, add a new "--state-branch" test which directly checks that a commit from the state branch is used when incrementally filtering a repo.
Tested-by: Michele Locati <michele@locati.it> Co-authored-by: Michele Locati <michele@locati.it> Signed-off-by: Michele Locati <michele@locati.it> Signed-off-by: Grant Moyer <dev@grantmoyer.com> --- git-filter-branch.sh | 4 +++- t/t7003-filter-branch.sh | 25 ++++++++++++++++++++++++- 2 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/git-filter-branch.sh b/git-filter-branch.sh index 24fa317aaa..9aa07be6e1 100755 --- a/git-filter-branch.sh +++ b/git-filter-branch.sh @@ -302,7 +302,9 @@ then do case "$line" in *:*) - echo "${line%:*}" >../map/"${line#*:}";; + from_commit=${line%:*} + to_commit=${line#*:} + echo "$to_commit" >../map/"$from_commit";; *) die "Unable to load state from $state_branch:filter.map";; esac diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh index 86011e7b1f..801cc83e5e 100755 --- a/t/t7003-filter-branch.sh +++ b/t/t7003-filter-branch.sh @@ -121,10 +121,33 @@ W=$(git rev-parse HEAD) test_expect_success 'using --state-branch to skip already rewritten commits' ' test_when_finished git reset --hard $V && git reset --hard $V && - git filter-branch --state-branch state -f --tree-filter "touch file || :" HEAD && + git filter-branch --state-branch state -f --tree-filter "exit 1" HEAD && test_cmp_rev $W HEAD ' +test_expect_success '--state-branch incremental rewrite uses the rewritten parents' ' + test_when_finished "rm -fr incremental" && + git init incremental && + ( + cd incremental && + mkdir sub && + test_commit first sub/file && + test_commit outside root-file && + git filter-branch --state-branch refs/state \ + --prune-empty --subdirectory-filter sub -- HEAD && + rewritten_first=$(git rev-parse HEAD) && + git reset --hard outside && + test_commit second sub/file && + git filter-branch -f --state-branch refs/state \ + --prune-empty --subdirectory-filter sub -- outside..HEAD && + test_cmp_rev $rewritten_first HEAD^ && + git show refs/state:filter.map >map && + echo "$(git rev-parse second):$(git rev-parse HEAD)" >expect && + grep "^$(git rev-parse second):" map >actual && + test_cmp expect actual + ) +' + git tag oldD HEAD~4 test_expect_success 'rewrite one branch, keeping a side branch' ' git branch modD oldD &&
-- 2.55.0