fsck: add a performance test for skipList

Create a performance test to see how the skipList implementation
performs. First we setup N bad commits, then we see how progressively
working our way up to 0..N in increments of 10x does. I.e. the
needle(s) in the haystack get progressively more numerous.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/perf/p1451-fsck-skip-list.sh b/t/perf/p1451-fsck-skip-list.sh
new file mode 100755 (executable)
index 0000000..c2b97d2
--- /dev/null
+++ b/t/perf/p1451-fsck-skip-list.sh
@@ -0,0 +1,40 @@
+#!/bin/sh
+
+test_description='Test fsck skipList performance'
+
+. ./perf-lib.sh
+
+test_perf_fresh_repo
+
+n=1000000
+
+test_expect_success "setup $n bad commits" '
+       for i in $(test_seq 1 $n)
+       do
+               echo "commit refs/heads/master" &&
+               echo "committer C <c@example.com> 1234567890 +0000" &&
+               echo "data <<EOF" &&
+               echo "$i.Q." &&
+               echo "EOF"
+       done | q_to_nul | git fast-import
+'
+
+skip=0
+while test $skip -le $n
+do
+       test_expect_success "create skipList for $skip bad commits" '
+               git log --format=%H --max-count=$skip |
+               sort >skiplist
+       '
+
+       test_perf "fsck with $skip skipped bad commits" '
+               git -c fsck.skipList=skiplist fsck
+       '
+
+       case $skip in
+       0) skip=1 ;;
+       *) skip=${skip}0 ;;
+       esac
+done
+
+test_done