On Wed, Nov 11, 2020 at 02:43:51PM -0500, Taylor Blau wrote:
> From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
>
> The bitmap_writer_build() method calls bitmap_builder_init() to
> construct a list of commits reachable from the selected commits along
> with a "reverse graph". This reverse graph has edges pointing from a
> commit to other commits that can reach that commit. After computing a
> reachability bitmap for a commit, the values in that bitmap are then
> copied to the reachability bitmaps across the edges in the reverse
> graph.
>
> We can now relax the role of the reverse graph to greatly reduce the
> number of intermediate reachability bitmaps we compute during this
> reverse walk. The end result is that we walk objects the same number of
> times as before when constructing the reachability bitmaps, but we also
> spend much less time copying bits between bitmaps and have much lower
> memory pressure in the process.
>
> The core idea is to select a set of "important" commits based on
> interactions among the sets of commits reachable from each selected commit.
This patch breaks the test 'truncated bitmap fails gracefully (ewah)'
when run with GIT_TEST_DEFAULT_HASH=sha256:
expecting success of 5310.66 'truncated bitmap fails gracefully (ewah)':
test_config pack.writebitmaphashcache false &&
git repack -ad &&
git rev-list --use-bitmap-index --count --all >expect &&
bitmap=$(ls .git/objects/pack/*.bitmap) &&
test_when_finished "rm -f $bitmap" &&
test_copy_bytes 256 <$bitmap >$bitmap.tmp &&
mv -f $bitmap.tmp $bitmap &&
git rev-list --use-bitmap-index --count --all >actual 2>stderr &&
test_cmp expect actual &&
test_i18ngrep corrupt.ewah.bitmap stderr
+ test_config pack.writebitmaphashcache false
+ git repack -ad
+ git rev-list --use-bitmap-index --count --all
+ ls .git/objects/pack/pack-23fe19963d67a1d4797a39622c15144bbf35ab76a2c0638ba9288cc688c24c16.bitmap
+ bitmap=.git/objects/pack/pack-23fe19963d67a1d4797a39622c15144bbf35ab76a2c0638ba9288cc688c24c16.bitmap
+ test_when_finished rm -f .git/objects/pack/pack-23fe19963d67a1d4797a39622c15144bbf35ab76a2c0638ba9288cc688c24c16.bitmap
+ test_copy_bytes 256
+ mv -f .git/objects/pack/pack-23fe19963d67a1d4797a39622c15144bbf35ab76a2c0638ba9288cc688c24c16.bitmap.tmp .git/objects/pack/pack-23fe19963d67a1d4797a39622c15144bbf35ab76a2c0638ba9288cc688c24c16.bitmap
+ git rev-list --use-bitmap-index --count --all
+ test_cmp expect actual
--- expect 2020-11-13 22:20:39.246355100 +0000
+++ actual 2020-11-13 22:20:39.254355294 +0000
@@ -1 +1 @@
-239
+236
error: last command exited with $?=1
