112 lines
3.8 KiB
Bash
Executable file
112 lines
3.8 KiB
Bash
Executable file
#!/bin/sh
|
|
|
|
test_description='test handling of inter-pack delta cycles during repack
|
|
|
|
The goal here is to create a situation where we have two blobs, A and B, with A
|
|
as a delta against B in one pack, and vice versa in the other. Then if we can
|
|
persuade a full repack to find A from one pack and B from the other, that will
|
|
give us a cycle when we attempt to reuse those deltas.
|
|
|
|
The trick is in the "persuade" step, as it depends on the internals of how
|
|
pack-objects picks which pack to reuse the deltas from. But we can assume
|
|
that it does so in one of two general strategies:
|
|
|
|
1. Using a static ordering of packs. In this case, no inter-pack cycles can
|
|
happen. Any objects with a delta relationship must be present in the same
|
|
pack (i.e., no "--thin" packs on disk), so we will find all related objects
|
|
from that pack. So assuming there are no cycles within a single pack (and
|
|
we avoid generating them via pack-objects or importing them via
|
|
index-pack), then our result will have no cycles.
|
|
|
|
So this case should pass the tests no matter how we arrange things.
|
|
|
|
2. Picking the next pack to examine based on locality (i.e., where we found
|
|
something else recently).
|
|
|
|
In this case, we want to make sure that we find the delta versions of A and
|
|
B and not their base versions. We can do this by putting two blobs in each
|
|
pack. The first is a "dummy" blob that can only be found in the pack in
|
|
question. And then the second is the actual delta we want to find.
|
|
|
|
The two blobs must be present in the same tree, not present in other trees,
|
|
and the dummy pathname must sort before the delta path.
|
|
|
|
The setup below focuses on case 2. We have two commits HEAD and HEAD^, each
|
|
which has two files: "dummy" and "file". Then we can make two packs which
|
|
contain:
|
|
|
|
[pack one]
|
|
HEAD:dummy
|
|
HEAD:file (as delta against HEAD^:file)
|
|
HEAD^:file (as base)
|
|
|
|
[pack two]
|
|
HEAD^:dummy
|
|
HEAD^:file (as delta against HEAD:file)
|
|
HEAD:file (as base)
|
|
|
|
Then no matter which order we start looking at the packs in, we know that we
|
|
will always find a delta for "file", because its lookup will always come
|
|
immediately after the lookup for "dummy".
|
|
'
|
|
. ./test-lib.sh
|
|
|
|
|
|
|
|
# Create a pack containing the tree $1 and blob $1:file, with
|
|
# the latter stored as a delta against $2:file.
|
|
#
|
|
# We convince pack-objects to make the delta in the direction of our choosing
|
|
# by marking $2 as a preferred-base edge. That results in $1:file as a thin
|
|
# delta, and index-pack completes it by adding $2:file as a base.
|
|
#
|
|
# Note that the two variants of "file" must be similar enough to convince git
|
|
# to create the delta.
|
|
make_pack () {
|
|
{
|
|
printf '%s\n' "-$(git rev-parse $2)"
|
|
printf '%s dummy\n' "$(git rev-parse $1:dummy)"
|
|
printf '%s file\n' "$(git rev-parse $1:file)"
|
|
} |
|
|
git pack-objects --stdout |
|
|
git index-pack --stdin --fix-thin
|
|
}
|
|
|
|
test_expect_success 'setup' '
|
|
test-tool genrandom base 4096 >base &&
|
|
for i in one two
|
|
do
|
|
# we want shared content here to encourage deltas...
|
|
cp base file &&
|
|
echo $i >>file &&
|
|
|
|
# ...whereas dummy should be short, because we do not want
|
|
# deltas that would create duplicates when we --fix-thin
|
|
echo $i >dummy &&
|
|
|
|
git add file dummy &&
|
|
test_tick &&
|
|
git commit -m $i ||
|
|
return 1
|
|
done &&
|
|
|
|
make_pack HEAD^ HEAD &&
|
|
make_pack HEAD HEAD^
|
|
'
|
|
|
|
test_expect_success 'repack' '
|
|
# We first want to check that we do not have any internal errors,
|
|
# and also that we do not hit the last-ditch cycle-breaking code
|
|
# in write_object(), which will issue a warning to stderr.
|
|
git repack -ad 2>stderr &&
|
|
test_must_be_empty stderr &&
|
|
|
|
# And then double-check that the resulting pack is usable (i.e.,
|
|
# we did not fail to notice any cycles). We know we are accessing
|
|
# the objects via the new pack here, because "repack -d" will have
|
|
# removed the others.
|
|
git cat-file blob HEAD:file >/dev/null &&
|
|
git cat-file blob HEAD^:file >/dev/null
|
|
'
|
|
|
|
test_done
|