git/stats: Surface information about reverse indices

Packfiles can have reverse indices that allow Git to easily map an
object location to its name in order to speed up some operations.
Report on the availability of this data structure as part of the
`PackfileInfo`.

Changelog: added

3 files changed, 22 insertions, 0 deletions

diff --git a/internal/git/housekeeping/optimize_repository.go b/internal/git/housekeeping/optimize_repository.go
index 1238e74f7..c0a248241 100644
--- a/internal/git/housekeeping/optimize_repository.go
+++ b/internal/git/housekeeping/optimize_repository.go
@@ -91,6 +91,7 @@ func (m *RepositoryManager) reportRepositoryInfo(ctx context.Context, info stats
 	m.reportDataStructureCount("loose_objects_stale_count", info.LooseObjects.StaleCount)
 	m.reportDataStructureCount("commit_graph_chain", info.CommitGraph.CommitGraphChainLength)
 	m.reportDataStructureCount("packfiles", info.Packfiles.Count)
+	m.reportDataStructureCount("packfiles_reverse_indices", info.Packfiles.ReverseIndexCount)
 	m.reportDataStructureCount("loose_references", info.References.LooseReferencesCount)
 
 	m.reportDataStructureSize("loose_objects", info.LooseObjects.Size)
diff --git a/internal/git/stats/repository_info.go b/internal/git/stats/repository_info.go
index 7ce5f2106..ddf974e49 100644
--- a/internal/git/stats/repository_info.go
+++ b/internal/git/stats/repository_info.go
@@ -241,6 +241,8 @@ type PackfilesInfo struct {
 	Count uint64 `json:"count"`
 	// Size is the total size of all loose objects in bytes, including stale ones.
 	Size uint64 `json:"size"`
+	// ReverseIndexCount is the number of reverse indices.
+	ReverseIndexCount uint64 `json:"reverse_index_count"`
 	// GarbageCount is the number of garbage files.
 	GarbageCount uint64 `json:"garbage_count"`
 	// GarbageSize is the total size of all garbage files in bytes.
@@ -290,6 +292,8 @@ func PackfilesInfoForRepository(repo *localrepo.Repo) (PackfilesInfo, error) {
 			if entryInfo.Size() > 0 {
 				info.Size += uint64(entryInfo.Size())
 			}
+		case hasPrefixAndSuffix(entryName, "pack-", ".rev"):
+			info.ReverseIndexCount++
 		case hasPrefixAndSuffix(entryName, "pack-", ".bitmap"):
 			bitmap, err := BitmapInfoForPath(filepath.Join(packfilesPath, entryName))
 			if err != nil {
diff --git a/internal/git/stats/repository_info_test.go b/internal/git/stats/repository_info_test.go
index f10e1096a..f58d55c6c 100644
--- a/internal/git/stats/repository_info_test.go
+++ b/internal/git/stats/repository_info_test.go
@@ -745,6 +745,23 @@ func TestPackfileInfoForRepository(t *testing.T) {
 			},
 		},
 		{
+			desc: "reverse index",
+			seedRepository: func(t *testing.T, repoPath string) {
+				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
+				gittest.Exec(t, cfg, "-c", "pack.writeReverseIndex=true", "-C", repoPath, "repack", "-Ad")
+			},
+			expectedInfo: PackfilesInfo{
+				Count:             1,
+				Size:              hashDependentSize(163, 189),
+				ReverseIndexCount: 1,
+				Bitmap: BitmapInfo{
+					Exists:       true,
+					Version:      1,
+					HasHashCache: true,
+				},
+			},
+		},
+		{
 			desc: "multi-pack-index",
 			seedRepository: func(t *testing.T, repoPath string) {
 				packfileDir := filepath.Join(repoPath, "objects", "pack")