From 1dc413ebe52bd5dffed63d69a0a239b7fb6ef699 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Tue, 19 Jan 2016 17:07:22 -0500 Subject: [PATCH] filter-branch: resolve $commit^{tree} in no-index case Commit 348d4f2 (filter-branch: skip index read/write when possible, 2015-11-06) taught filter-branch to optimize out the final "git write-tree" when we know we haven't touched the tree with any of our filters. It does by simply putting the literal text "$commit^{tree}" into the "$tree" variable, avoiding a useless rev-parse call. However, when we pass this to git_commit_non_empty_tree(), it gets confused; it resolves "$commit^{tree}" itself, and compares our string to the 40-hex sha1, which obviously doesn't match. As a result, "--prune-empty" (or any custom filter using git_commit_non_empty_tree) will fail to drop an empty commit (when filter-branch is used without a tree or index filter). Let's resolve $tree to the 40-hex ourselves, so that git_commit_non_empty_tree can work. Unfortunately, this is a bit slower due to the extra process overhead: $ cd t/perf && ./run 348d4f2 HEAD p7000-filter-branch.sh [...] Test 348d4f2 HEAD -------------------------------------------------------------- 7000.2: noop filter 3.76(0.24+0.26) 4.54(0.28+0.24) +20.7% We could try to make git_commit_non_empty_tree more clever. However, the value of $tree here is technically user-visible. The user can provide arbitrary shell code at this stage, which could itself have a similar assumption to what is in git_commit_non_empty_tree. So the conservative choice to fix this regression is to take the 20% hit and give the pre-348d4f2 behavior. We still end up much faster than before the optimization: $ cd t/perf && ./run 348d4f2^ HEAD p7000-filter-branch.sh [...] Test 348d4f2^ HEAD -------------------------------------------------------------- 7000.2: noop filter 9.51(4.32+0.40) 4.51(0.28+0.23) -52.6% Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- git-filter-branch.sh | 2 +- t/t7003-filter-branch.sh | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/git-filter-branch.sh b/git-filter-branch.sh index d61f9baceb..5e094ce18d 100755 --- a/git-filter-branch.sh +++ b/git-filter-branch.sh @@ -404,7 +404,7 @@ while read commit parents; do then tree=$(git write-tree) else - tree="$commit^{tree}" + tree=$(git rev-parse "$commit^{tree}") fi workdir=$workdir @SHELL_PATH@ -c "$filter_commit" "git commit-tree" \ "$tree" $parentstr < ../message > ../map/$commit || diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh index 377c648e04..97c23c2e31 100755 --- a/t/t7003-filter-branch.sh +++ b/t/t7003-filter-branch.sh @@ -333,6 +333,14 @@ test_expect_success 'prune empty collapsed merges' ' test_cmp expect actual ' +test_expect_success 'prune empty works even without index/tree filters' ' + git rev-list HEAD >expect && + git commit --allow-empty -m empty && + git filter-branch -f --prune-empty HEAD && + git rev-list HEAD >actual && + test_cmp expect actual +' + test_expect_success '--remap-to-ancestor with filename filters' ' git checkout master && git reset --hard A &&