Merge branch 'ac/bitmap-lookup-table'

The pack bitmap file gained a bitmap-lookup table to speed up
locating the necessary bitmap for a given commit.

* ac/bitmap-lookup-table:
  pack-bitmap-write: drop unused pack_idx_entry parameters
  bitmap-lookup-table: add performance tests for lookup table
  pack-bitmap: prepare to read lookup table extension
  pack-bitmap-write: learn pack.writeBitmapLookupTable and add tests
  pack-bitmap-write.c: write lookup table extension
  bitmap: move `get commit positions` code to `bitmap_writer_finish`
  Documentation/technical: describe bitmap lookup table extension

1 files changed, 31 insertions, 0 deletions

diff --git a/t/perf/lib-bitmap.sh b/t/perf/lib-bitmap.sh
index 63d3bc7cec..55a8feb1dc 100644
--- a/t/perf/lib-bitmap.sh
+++ b/t/perf/lib-bitmap.sh
@@ -67,3 +67,34 @@ test_partial_bitmap () {
 			--filter=tree:0 >/dev/null
 	'
 }
+
+test_pack_bitmap () {
+	test_perf "repack to disk" '
+		git repack -ad
+	'
+
+	test_full_bitmap
+
+	test_expect_success "create partial bitmap state" '
+		# pick a commit to represent the repo tip in the past
+		cutoff=$(git rev-list HEAD~100 -1) &&
+		orig_tip=$(git rev-parse HEAD) &&
+
+		# now kill off all of the refs and pretend we had
+		# just the one tip
+		rm -rf .git/logs .git/refs/* .git/packed-refs &&
+		git update-ref HEAD $cutoff &&
+
+		# and then repack, which will leave us with a nice
+		# big bitmap pack of the "old" history, and all of
+		# the new history will be loose, as if it had been pushed
+		# up incrementally and exploded via unpack-objects
+		git repack -Ad &&
+
+		# and now restore our original tip, as if the pushes
+		# had happened
+		git update-ref HEAD $orig_tip
+	'
+
+	test_partial_bitmap
+}