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Diffstat (limited to 't/t5316-pack-delta-depth.sh')
| -rwxr-xr-x | t/t5316-pack-delta-depth.sh | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/t/t5316-pack-delta-depth.sh b/t/t5316-pack-delta-depth.sh new file mode 100755 index 0000000..eb4ef3d --- /dev/null +++ b/t/t5316-pack-delta-depth.sh @@ -0,0 +1,121 @@ +#!/bin/sh + +test_description='pack-objects breaks long cross-pack delta chains' + +TEST_PASSES_SANITIZE_LEAK=true +. ./test-lib.sh + +# This mirrors a repeated push setup: +# +# 1. A client repeatedly modifies some files, makes a +# commit, and pushes the result. It does this N times +# before we get around to repacking. +# +# 2. Each push generates a thin pack with the new version of +# various objects. Let's consider some file in the root tree +# which is updated in each commit. +# +# When generating push number X, we feed commit X-1 (and +# thus blob X-1) as a preferred base. The resulting pack has +# blob X as a thin delta against blob X-1. +# +# On the receiving end, "index-pack --fix-thin" will +# complete the pack with a base copy of blob X-1. +# +# 3. In older versions of git, if we used the delta from +# pack X, then we'd always find blob X-1 as a base in the +# same pack (and generate a fresh delta). +# +# But with the pack mru, we jump from delta to delta +# following the traversal order: +# +# a. We grab blob X from pack X as a delta, putting it at +# the tip of our mru list. +# +# b. Eventually we move onto commit X-1. We need other +# objects which are only in pack X-1 (in the test code +# below, it's the containing tree). That puts pack X-1 +# at the tip of our mru list. +# +# c. Eventually we look for blob X-1, and we find the +# version in pack X-1 (because it's the mru tip). +# +# Now we have blob X as a delta against X-1, which is a delta +# against X-2, and so forth. +# +# In the real world, these small pushes would get exploded by +# unpack-objects rather than "index-pack --fix-thin", but the +# same principle applies to larger pushes (they only need one +# repeatedly-modified file to generate the delta chain). + +test_expect_success 'create series of packs' ' + test-tool genrandom foo 4096 >content && + prev= && + for i in $(test_seq 1 10) + do + cat content >file && + echo $i >>file && + git add file && + git commit -m $i && + cur=$(git rev-parse HEAD^{tree}) && + { + if test -n "$prev" + then + echo "-$prev" + fi && + echo $cur && + echo "$(git rev-parse :file) file" + } | git pack-objects --stdout >tmp && + GIT_TRACE2_EVENT=$PWD/trace \ + git index-pack -v --stdin --fix-thin <tmp || return 1 && + grep -c region_enter.*progress trace >enter && + grep -c region_leave.*progress trace >leave && + test_cmp enter leave && + prev=$cur + done +' + +max_chain() { + git index-pack --verify-stat-only "$1" >output && + perl -lne ' + BEGIN { $len = 0 } + /chain length = (\d+)/ and $len = $1; + END { print $len } + ' output +} + +# Note that this whole setup is pretty reliant on the current +# packing heuristics. We double-check that our test case +# actually produces a long chain. If it doesn't, it should be +# adjusted (or scrapped if the heuristics have become too unreliable) +test_expect_success 'packing produces a long delta' ' + # Use --window=0 to make sure we are seeing reused deltas, + # not computing a new long chain. + pack=$(git pack-objects --all --window=0 </dev/null pack) && + echo 9 >expect && + max_chain pack-$pack.pack >actual && + test_cmp expect actual +' + +test_expect_success '--depth limits depth' ' + pack=$(git pack-objects --all --depth=5 </dev/null pack) && + echo 5 >expect && + max_chain pack-$pack.pack >actual && + test_cmp expect actual +' + +test_expect_success '--depth=0 disables deltas' ' + pack=$(git pack-objects --all --depth=0 </dev/null pack) && + echo 0 >expect && + max_chain pack-$pack.pack >actual && + test_cmp expect actual +' + +test_expect_success 'negative depth disables deltas' ' + pack=$(git pack-objects --all --depth=-1 </dev/null pack) && + echo 0 >expect && + max_chain pack-$pack.pack >actual && + test_cmp expect actual +' + +test_done |