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125c32605a
When reusing chunks verbatim from an existing source pack, the function
write_reused_pack() first attempts to reuse whole words (via the
function `write_reused_pack_verbatim()`), and then individual bits (via
`write_reused_pack_one()`).
In the non-MIDX case, all of this code works fine. Likewise, in the MIDX
case, processing bits individually from the first (preferred) pack works
fine. However, processing subsequent packs in the MIDX case is broken
when there are duplicate objects among the set of MIDX'd packs.
This is because we treat the individual bit positions as valid pack
positions within the source pack(s), which does not account for gaps in
the source pack, like we see when the MIDX must break ties between
duplicate objects which appear in multiple packs.
The broken code looks like:
for (; i < reuse_packfile_bitmap->word_alloc; i++) {
for (offset = 0; offset < BITS_IN_EWORD, offset++) {
/* ... */
write_reused_pack_one(reuse_packfile->p,
pos + offset - reuse_packfile->bitmap_pos,
f, pack_start, &w_curs);
}
}
, where the second argument is incorrect and does not account for gaps.
Instead, make sure that we translate bit positions in the MIDX's
pseudo-pack order to pack positions in the respective source packs by:
- Translating the bit position (pseudo-pack order) to a MIDX position
(lexical order).
- Use the MIDX position to obtain the offset at which the given object
occurs in the source pack.
- Then translate that offset back into a pack relative position within
the source pack by calling offset_to_pack_pos().
After doing this, then we can safely use the result as a pack position.
Note that when doing single-pack reuse, as well as reusing objects from
the MIDX's preferred pack, such translation is not necessary, since
either ties are broken in favor of the preferred pack, or there are no
ties to break at all (in the case of non-MIDX bitmaps).
Failing to do this can result in strange failure modes. One example that
can occur when misinterpreting bits in the above fashion is that Git
thinks it's supposed to send a delta that the caller does not want.
Under this (incorrect) assumption, we try to look up the delta's base
(so that we can patch any OFS_DELTAs if necessary). We do this using
find_reused_offset().
But if we try and call that function for an offset belonging to an
object we did not send, we'll get back garbage. This can result in us
computing a negative fixup value, which results in memory corruption
when trying to write the (patched) OFS_DELTA header.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
262 lines
6.3 KiB
Bash
Executable file
262 lines
6.3 KiB
Bash
Executable file
#!/bin/sh
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test_description='pack-objects multi-pack reuse'
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TEST_PASSES_SANITIZE_LEAK=true
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. ./test-lib.sh
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. "$TEST_DIRECTORY"/lib-bitmap.sh
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GIT_TEST_MULTI_PACK_INDEX=0
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GIT_TEST_MULTI_PACK_INDEX_WRITE_INCREMENTAL=0
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objdir=.git/objects
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packdir=$objdir/pack
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test_pack_reused () {
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test_trace2_data pack-objects pack-reused "$1"
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}
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test_packs_reused () {
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test_trace2_data pack-objects packs-reused "$1"
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}
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# pack_position <object> </path/to/pack.idx
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pack_position () {
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git show-index >objects &&
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grep "$1" objects | cut -d" " -f1
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}
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# test_pack_objects_reused_all <pack-reused> <packs-reused>
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test_pack_objects_reused_all () {
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: >trace2.txt &&
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GIT_TRACE2_EVENT="$PWD/trace2.txt" \
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git pack-objects --stdout --revs --all --delta-base-offset \
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>got.pack &&
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test_pack_reused "$1" <trace2.txt &&
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test_packs_reused "$2" <trace2.txt &&
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git index-pack --strict -o got.idx got.pack
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}
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# test_pack_objects_reused <pack-reused> <packs-reused>
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test_pack_objects_reused () {
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: >trace2.txt &&
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GIT_TRACE2_EVENT="$PWD/trace2.txt" \
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git pack-objects --stdout --revs >got.pack &&
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test_pack_reused "$1" <trace2.txt &&
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test_packs_reused "$2" <trace2.txt &&
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git index-pack --strict -o got.idx got.pack
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}
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test_expect_success 'preferred pack is reused for single-pack reuse' '
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test_config pack.allowPackReuse single &&
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for i in A B
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do
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test_commit "$i" &&
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git repack -d || return 1
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done &&
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git multi-pack-index write --bitmap &&
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test_pack_objects_reused_all 3 1
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'
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test_expect_success 'multi-pack reuse is disabled by default' '
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test_pack_objects_reused_all 3 1
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'
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test_expect_success 'feature.experimental implies multi-pack reuse' '
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test_config feature.experimental true &&
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test_pack_objects_reused_all 6 2
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'
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test_expect_success 'multi-pack reuse can be disabled with feature.experimental' '
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test_config feature.experimental true &&
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test_config pack.allowPackReuse single &&
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test_pack_objects_reused_all 3 1
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'
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test_expect_success 'enable multi-pack reuse' '
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git config pack.allowPackReuse multi
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'
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test_expect_success 'reuse all objects from subset of bitmapped packs' '
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test_commit C &&
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git repack -d &&
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git multi-pack-index write --bitmap &&
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cat >in <<-EOF &&
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$(git rev-parse C)
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^$(git rev-parse A)
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EOF
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test_pack_objects_reused 6 2 <in
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'
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test_expect_success 'reuse all objects from all packs' '
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test_pack_objects_reused_all 9 3
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'
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test_expect_success 'reuse objects from first pack with middle gap' '
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for i in D E F
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do
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test_commit "$i" || return 1
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done &&
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# Set "pack.window" to zero to ensure that we do not create any
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# deltas, which could alter the amount of pack reuse we perform
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# (if, for e.g., we are not sending one or more bases).
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D="$(git -c pack.window=0 pack-objects --all --unpacked $packdir/pack)" &&
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d_pos="$(pack_position $(git rev-parse D) <$packdir/pack-$D.idx)" &&
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e_pos="$(pack_position $(git rev-parse E) <$packdir/pack-$D.idx)" &&
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f_pos="$(pack_position $(git rev-parse F) <$packdir/pack-$D.idx)" &&
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# commits F, E, and D, should appear in that order at the
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# beginning of the pack
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test $f_pos -lt $e_pos &&
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test $e_pos -lt $d_pos &&
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# Ensure that the pack we are constructing sorts ahead of any
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# other packs in lexical/bitmap order by choosing it as the
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# preferred pack.
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git multi-pack-index write --bitmap --preferred-pack="pack-$D.idx" &&
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cat >in <<-EOF &&
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$(git rev-parse E)
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^$(git rev-parse D)
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EOF
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test_pack_objects_reused 3 1 <in
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'
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test_expect_success 'reuse objects from middle pack with middle gap' '
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rm -fr $packdir/multi-pack-index* &&
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# Ensure that the pack we are constructing sort into any
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# position *but* the first one, by choosing a different pack as
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# the preferred one.
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git multi-pack-index write --bitmap --preferred-pack="pack-$A.idx" &&
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cat >in <<-EOF &&
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$(git rev-parse E)
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^$(git rev-parse D)
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EOF
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test_pack_objects_reused 3 1 <in
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'
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test_expect_success 'omit delta with uninteresting base (same pack)' '
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git repack -adk &&
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test_seq 32 >f &&
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git add f &&
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test_tick &&
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git commit -m "delta" &&
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delta="$(git rev-parse HEAD)" &&
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test_seq 64 >f &&
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test_tick &&
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git commit -a -m "base" &&
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base="$(git rev-parse HEAD)" &&
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test_commit other &&
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git repack -d &&
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have_delta "$(git rev-parse $delta:f)" "$(git rev-parse $base:f)" &&
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git multi-pack-index write --bitmap &&
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cat >in <<-EOF &&
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$(git rev-parse other)
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^$base
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EOF
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# We can only reuse the 3 objects corresponding to "other" from
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# the latest pack.
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#
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# This is because even though we want "delta", we do not want
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# "base", meaning that we have to inflate the delta/base-pair
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# corresponding to the blob in commit "delta", which bypasses
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# the pack-reuse mechanism.
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#
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# The remaining objects from the other pack are similarly not
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# reused because their objects are on the uninteresting side of
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# the query.
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test_pack_objects_reused 3 1 <in
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'
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test_expect_success 'omit delta from uninteresting base (cross pack)' '
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cat >in <<-EOF &&
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$(git rev-parse $base)
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^$(git rev-parse $delta)
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EOF
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P="$(git pack-objects --revs $packdir/pack <in)" &&
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git multi-pack-index write --bitmap --preferred-pack="pack-$P.idx" &&
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packs_nr="$(find $packdir -type f -name "pack-*.pack" | wc -l)" &&
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objects_nr="$(git rev-list --count --all --objects)" &&
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test_pack_objects_reused_all $(($objects_nr - 1)) $packs_nr
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'
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test_expect_success 'non-omitted delta in MIDX preferred pack' '
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test_config pack.allowPackReuse single &&
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cat >p1.objects <<-EOF &&
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$(git rev-parse $base)
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^$(git rev-parse $delta^)
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EOF
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cat >p2.objects <<-EOF &&
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$(git rev-parse F)
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EOF
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p1="$(git pack-objects --revs $packdir/pack <p1.objects)" &&
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p2="$(git pack-objects --revs $packdir/pack <p2.objects)" &&
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cat >in <<-EOF &&
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pack-$p1.idx
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pack-$p2.idx
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EOF
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git multi-pack-index write --bitmap --stdin-packs \
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--preferred-pack=pack-$p1.pack <in &&
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git show-index <$packdir/pack-$p1.idx >expect &&
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test_pack_objects_reused_all $(wc -l <expect) 1
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'
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test_expect_success 'duplicate objects' '
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git init duplicate-objects &&
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(
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cd duplicate-objects &&
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git config pack.allowPackReuse multi &&
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test_commit base &&
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git repack -a &&
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git rev-parse HEAD^{tree} >in &&
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p="$(git pack-objects $packdir/pack <in)" &&
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git multi-pack-index write --bitmap --preferred-pack=pack-$p.idx &&
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objects_nr="$(git rev-list --count --all --objects)" &&
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packs_nr="$(find $packdir -type f -name "pack-*.pack" | wc -l)" &&
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test_pack_objects_reused_all $objects_nr $packs_nr
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)
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'
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test_done
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