midx.c: prevent `expire` from removing the cruft pack

The `expire` sub-command unlinks any packs that are (a) contained in the
MIDX, but (b) have no objects referenced by the MIDX.

This sub-command ignores `.keep` packs, which remain on-disk even if
they have no objects referenced by the MIDX. Cruft packs, however,
aren't given the same treatment: if none of the objects contained in the
cruft pack are selected from the cruft pack by the MIDX, then the cruft
pack is eligible to be expired.

This is less than desireable, since the cruft pack has important
metadata about the individual object mtimes, which is useful to
determine how quickly an object should age out of the repository when
pruning.

Ordinarily, we wouldn't expect the contents of a cruft pack to
duplicated across non-cruft packs (and we'd expect to see the MIDX
select all cruft objects from other sources even less often). But
nonetheless, it is still possible to trick the `expire` sub-command into
removing the `.mtimes` file in this circumstance.

Teach the `expire` sub-command to ignore cruft packs in the same manner
as it does `.keep` packs, in order to keep their metadata around, even
when they are unreferenced by the MIDX.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-multi-pack-index.txt b/Documentation/git-multi-pack-index.txt
index 11e6dc53e3bbe91d4c8caa955f60da63967bf0d1..3696506eb355e1b11a447a7014dcca370b760555 100644 (file)
--- a/Documentation/git-multi-pack-index.txt
+++ b/Documentation/git-multi-pack-index.txt
@@ -72,8 +72,8 @@ verify::
 expire::
        Delete the pack-files that are tracked by the MIDX file, but
        have no objects referenced by the MIDX (with the exception of
-       `.keep` packs). Rewrite the MIDX file afterward to remove all
-       references to these pack-files.
+       `.keep` packs and cruft packs). Rewrite the MIDX file afterward
+       to remove all references to these pack-files.
 
 repack::
        Create a new pack-file containing objects in small pack-files

diff --git a/midx.c b/midx.c
index c27d0e5f1510c32ad7cbf0fca8dc1d05ec4917a3..bff5b999333c6f390da6e23c2842af32d1793dca 100644 (file)
--- a/midx.c
+++ b/midx.c
@@ -1839,7 +1839,7 @@ int expire_midx_packs(struct repository *r, const char *object_dir, unsigned fla
                if (prepare_midx_pack(r, m, i))
                        continue;
 
-               if (m->packs[i]->pack_keep)
+               if (m->packs[i]->pack_keep || m->packs[i]->is_cruft)
                        continue;
 
                pack_name = xstrdup(m->packs[i]->pack_name);

diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
index afbe93f162e854b462774cd5242ddfe40a64bf6c..2d51b0968012fd1f5b8e57a5f323bbe58ba686e4 100755 (executable)
--- a/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@ -847,6 +847,36 @@ test_expect_success 'expire respects .keep files' '
        )
 '
 
+test_expect_success 'expiring unreferenced cruft pack retains pack' '
+       git init repo &&
+       test_when_finished "rm -fr repo" &&
+       (
+               cd repo &&
+
+               test_commit base &&
+               test_commit --no-tag unreachable &&
+               unreachable=$(git rev-parse HEAD) &&
+
+               git reset --hard base &&
+               git reflog expire --all --expire=all &&
+               git repack --cruft -d &&
+               mtimes="$(ls $objdir/pack/pack-*.mtimes)" &&
+
+               echo "base..$unreachable" >in &&
+               pack="$(git pack-objects --revs --delta-base-offset \
+                       $objdir/pack/pack <in)" &&
+
+               # Preferring the contents of "$pack" will leave the
+               # cruft pack unreferenced (ie., none of the objects
+               # contained in the cruft pack will have their MIDX copy
+               # selected from the cruft pack).
+               git multi-pack-index write --preferred-pack="pack-$pack.pack" &&
+               git multi-pack-index expire &&
+
+               test_path_is_file "$mtimes"
+       )
+'
+
 test_expect_success 'repack --batch-size=0 repacks everything' '
        cp -r dup dup2 &&
        (