revlist: ignore all objects reachable from ignored objects

Usually we call revlist.Objects ignoring a set of commits.
This is not enough to ignore everything reachable from such
set, so we first get all objects reachable from the ignored
set and then walk the tree again ignoring that new set.

Author: smola

plumbing/revlist/revlist.go

@@ -16,7 +16,26 @@ import (
 // the reachable objects from the given objects. Ignore param are object hashes
 // that we want to ignore on the result. All that objects must be accessible
 // from the object storer.
-func Objects(s storer.EncodedObjectStorer, objects, ignore []plumbing.Hash) ([]plumbing.Hash, error) {
+func Objects(
+	s storer.EncodedObjectStorer,
+	objs,
+	ignore []plumbing.Hash,
+) ([]plumbing.Hash, error) {
+	ignore, err := objects(s, ignore, nil, true)
+	if err != nil {
+		return nil, err
+	}
+
+	return objects(s, objs, ignore, false)
+}
+
+func objects(
+	s storer.EncodedObjectStorer,
+	objects,
+	ignore []plumbing.Hash,
+	allowMissingObjects bool,
+) ([]plumbing.Hash, error) {
+
 	seen := hashListToSet(ignore)
 	result := make(map[plumbing.Hash]bool)
 
@@ -29,6 +48,10 @@ func Objects(s storer.EncodedObjectStorer, objects, ignore []plumbing.Hash) ([]p
 
 	for _, h := range objects {
 		if err := processObject(s, h, seen, ignore, walkerFunc); err != nil {
+			if allowMissingObjects && err == plumbing.ErrObjectNotFound {
+				continue
+			}
+
 			return nil, err
 		}
 	}
@@ -44,6 +67,10 @@ func processObject(
 	ignore []plumbing.Hash,
 	walkerFunc func(h plumbing.Hash),
 ) error {
+	if seen[h] {
+		return nil
+	}
+
 	o, err := s.EncodedObject(plumbing.AnyObject, h)
 	if err != nil {
 		return err