revlist: do not revisit ancestors as long as all branches are visited

plumbing/revlist/revlist.go

@@ -37,6 +37,7 @@ func objects(
 ) ([]plumbing.Hash, error) {
 	seen := hashListToSet(ignore)
 	result := make(map[plumbing.Hash]bool)
+	visited := make(map[plumbing.Hash]bool)
 
 	walkerFunc := func(h plumbing.Hash) {
 		if !seen[h] {
@@ -46,7 +47,7 @@ func objects(
 	}
 
 	for _, h := range objects {
-		if err := processObject(s, h, seen, ignore, walkerFunc); err != nil {
+		if err := processObject(s, h, seen, visited, ignore, walkerFunc); err != nil {
 			if allowMissingObjects && err == plumbing.ErrObjectNotFound {
 				continue
 			}
@@ -63,6 +64,7 @@ func processObject(
 	s storer.EncodedObjectStorer,
 	h plumbing.Hash,
 	seen map[plumbing.Hash]bool,
+	visited map[plumbing.Hash]bool,
 	ignore []plumbing.Hash,
 	walkerFunc func(h plumbing.Hash),
 ) error {
@@ -82,12 +84,12 @@ func processObject(
 
 	switch do := do.(type) {
 	case *object.Commit:
-		return reachableObjects(do, seen, ignore, walkerFunc)
+		return reachableObjects(do, seen, visited, ignore, walkerFunc)
 	case *object.Tree:
 		return iterateCommitTrees(seen, do, walkerFunc)
 	case *object.Tag:
 		walkerFunc(do.Hash)
-		return processObject(s, do.Target, seen, ignore, walkerFunc)
+		return processObject(s, do.Target, seen, visited, ignore, walkerFunc)
 	case *object.Blob:
 		walkerFunc(do.Hash)
 	default:
@@ -105,10 +107,14 @@ func processObject(
 func reachableObjects(
 	commit *object.Commit,
 	seen map[plumbing.Hash]bool,
+	visited map[plumbing.Hash]bool,
 	ignore []plumbing.Hash,
 	cb func(h plumbing.Hash),
 ) error {
 	i := object.NewCommitPreorderIter(commit, seen, ignore)
+	pending := make(map[plumbing.Hash]bool)
+	addPendingParents(pending, visited, commit)
+
 	for {
 		commit, err := i.Next()
 		if err == io.EOF {
@@ -119,6 +125,16 @@ func reachableObjects(
 			return err
 		}
 
+		if pending[commit.Hash] {
+			delete(pending, commit.Hash)
+		}
+
+		addPendingParents(pending, visited, commit)
+
+		if visited[commit.Hash] && len(pending) == 0 {
+			break
+		}
+
 		if seen[commit.Hash] {
 			continue
 		}
@@ -138,6 +154,14 @@ func reachableObjects(
 	return nil
 }
 
+func addPendingParents(pending, visited map[plumbing.Hash]bool, commit *object.Commit) {
+	for _, p := range commit.ParentHashes {
+		if !visited[p] {
+			pending[p] = true
+		}
+	}
+}
+
 // iterateCommitTrees iterate all reachable trees from the given commit
 func iterateCommitTrees(
 	seen map[plumbing.Hash]bool,

plumbing/revlist/revlist_test.go

@@ -217,3 +217,60 @@ func (s *RevListSuite) TestRevListObjectsNewBranch(c *C) {
 	}
 	c.Assert(len(remoteHist), Equals, len(revList))
 }
+
+// This tests will ensure that a5b8b09 and b8e471f will be visited even if
+// 35e8510 has already been visited and will not stop iterating until they
+// have been as well.
+//
+// * af2d6a6 some json
+// *   1669dce Merge branch 'master'
+// |\
+// | *   a5b8b09 Merge pull request #1
+// | |\
+// | | * b8e471f Creating changelog
+// | |/
+// * | 35e8510 binary file
+// |/
+// * b029517 Initial commit
+func (s *RevListSuite) TestReachableObjectsNoRevisit(c *C) {
+	obj, err := s.Storer.EncodedObject(plumbing.CommitObject, plumbing.NewHash("af2d6a6954d532f8ffb47615169c8fdf9d383a1a"))
+	c.Assert(err, IsNil)
+
+	do, err := object.DecodeObject(s.Storer, obj)
+	c.Assert(err, IsNil)
+
+	commit, ok := do.(*object.Commit)
+	c.Assert(ok, Equals, true)
+
+	var visited []plumbing.Hash
+	err = reachableObjects(
+		commit,
+		map[plumbing.Hash]bool{
+			plumbing.NewHash("35e85108805c84807bc66a02d91535e1e24b38b9"): true,
+		},
+		map[plumbing.Hash]bool{
+			plumbing.NewHash("35e85108805c84807bc66a02d91535e1e24b38b9"): true,
+		},
+		nil,
+		func(h plumbing.Hash) {
+			obj, err := s.Storer.EncodedObject(plumbing.AnyObject, h)
+			c.Assert(err, IsNil)
+
+			do, err := object.DecodeObject(s.Storer, obj)
+			c.Assert(err, IsNil)
+
+			if _, ok := do.(*object.Commit); ok {
+				visited = append(visited, h)
+			}
+		},
+	)
+	c.Assert(err, IsNil)
+
+	c.Assert(visited, DeepEquals, []plumbing.Hash{
+		plumbing.NewHash("af2d6a6954d532f8ffb47615169c8fdf9d383a1a"),
+		plumbing.NewHash("1669dce138d9b841a518c64b10914d88f5e488ea"),
+		plumbing.NewHash("a5b8b09e2f8fcb0bb99d3ccb0958157b40890d69"),
+		plumbing.NewHash("b029517f6300c2da0f4b651b8642506cd6aaf45d"),
+		plumbing.NewHash("b8e471f58bcbca63b07bda20e428190409c2db47"),
+	})
+}