Merge pull request #2195 from libgit2/cmn/revwalk-no-hide

revwalk: don't try to find merge bases when there can be none

src/merge.c

@@ -205,6 +205,12 @@ int git_merge__bases_many(git_commit_list **out, git_revwalk *walk, git_commit_l
 	git_commit_list *result = NULL, *tmp = NULL;
 	git_pqueue list;
 
+	/* If there's only the one commit, there can be no merge bases */
+	if (twos->length == 0) {
+		*out = NULL;
+		return 0;
+	}
+
 	/* if the commit is repeated, we have a our merge base already */
 	git_vector_foreach(twos, i, two) {
 		if (one == two)

src/revwalk.c

@@ -141,6 +141,9 @@ static int push_commit(git_revwalk *walk, const git_oid *oid, int uninteresting,
 	if (commit == NULL)
 		return -1; /* error already reported by failed lookup */
 
+	if (uninteresting)
+		walk->did_hide = 1;
+
 	commit->uninteresting = uninteresting;
 	if (walk->one == NULL && !uninteresting) {
 		walk->one = commit;
@@ -390,11 +393,18 @@ static int prepare_walk(git_revwalk *walk)
 		return GIT_ITEROVER;
 	}
 
-	/* first figure out what the merge bases are */
-	if (git_merge__bases_many(&bases, walk, walk->one, &walk->twos) < 0)
-		return -1;
+	/*
+	 * If the user asked to hide commits, we need to figure out
+	 * what the merge bases are so we can know when we can stop
+	 * marking parents uninteresting.
+	 */
+	if (walk->did_hide) {
+		if (git_merge__bases_many(&bases, walk, walk->one, &walk->twos) < 0)
+			return -1;
+
+		git_commit_list_free(&bases);
+	}
 
-	git_commit_list_free(&bases);
 	if (process_commit(walk, walk->one, walk->one->uninteresting) < 0)
 		return -1;
 

src/revwalk.h

@@ -32,7 +32,8 @@ struct git_revwalk {
 	int (*enqueue)(git_revwalk *, git_commit_list_node *);
 
 	unsigned walking:1,
-		first_parent: 1;
+		first_parent: 1,
+		did_hide: 1;
 	unsigned int sorting;
 
 	/* merge base calculation */