Fix small memory leaks induced by diff_tree_setup_paths

Run diff_tree_release_paths in the appropriate places, and add a test to
avoid NULL dereference. Better safe than sorry.

Signed-off-by: Mike Hommey <mh@glandium.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-blame.c

@@ -388,6 +388,7 @@ static struct origin *find_origin(struct scoreboard *sb,
 		}
 	}
 	diff_flush(&diff_opts);
+	diff_tree_release_paths(&diff_opts);
 	if (porigin) {
 		/*
 		 * Create a freestanding copy that is not part of
@@ -444,6 +445,7 @@ static struct origin *find_rename(struct scoreboard *sb,
 		}
 	}
 	diff_flush(&diff_opts);
+	diff_tree_release_paths(&diff_opts);
 	return porigin;
 }
 
@@ -1165,7 +1167,7 @@ static int find_copy_in_parent(struct scoreboard *sb,
 		}
 	}
 	diff_flush(&diff_opts);
-
+	diff_tree_release_paths(&diff_opts);
 	return retval;
 }
 

builtin-reset.c

@@ -158,6 +158,7 @@ static int read_from_tree(const char *prefix, const char **argv,
 		return 1;
 	diffcore_std(&opt);
 	diff_flush(&opt);
+	diff_tree_release_paths(&opt);
 
 	if (!index_was_discarded)
 		/* The index is still clobbered from do_diff_cache() */

tree-diff.c

@@ -326,6 +326,7 @@ static void try_to_follow_renames(struct tree_desc *t1, struct tree_desc *t2, co
 		die("unable to set up diff options to follow renames");
 	diff_tree(t1, t2, base, &diff_opts);
 	diffcore_std(&diff_opts);
+	diff_tree_release_paths(&diff_opts);
 
 	/* Go through the new set of filepairing, and see if we find a more interesting one */
 	for (i = 0; i < q->nr; i++) {
@@ -342,6 +343,7 @@ static void try_to_follow_renames(struct tree_desc *t1, struct tree_desc *t2, co
 			choice = p;
 
 			/* Update the path we use from now on.. */
+			diff_tree_release_paths(opt);
 			opt->paths[0] = xstrdup(p->one->path);
 			diff_tree_setup_paths(opt->paths, opt);
 			break;