Merge branch 'js/read-tree' into js/c-merge-recursive

* js/read-tree: (107 commits)
  read-tree: move merge functions to the library
  read-trees: refactor the unpack_trees() part
  tar-tree: illustrate an obscure feature better
  git.c: allow alias expansion without a git directory
  setup_git_directory_gently: do not barf when GIT_DIR is given.
  Build on Debian GNU/kFreeBSD
  Call setup_git_directory() much earlier
  Call setup_git_directory() early
  Display an error from update-ref if target ref name is invalid.
  Fix http-fetch
  t4103: fix binary patch application test.
  git-apply -R: binary patches are irreversible for now.
  Teach git-apply about '-R'
  Makefile: ssh-pull.o depends on ssh-fetch.c
  log and diff family: honor config even from subdirectories
  git-reset: detect update-ref error and report it.
  lost-found: use fsck-objects --full
  Teach git-http-fetch the --stdin switch
  Teach git-local-fetch the --stdin switch
  Make pull() support fetching multiple targets at once
  ...

1 files changed, 11 insertions, 3 deletions

diff --git a/builtin-diff.c b/builtin-diff.c
index cb38f44561..48d2fd03b7 100644
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -221,7 +221,7 @@ void add_head(struct rev_info *revs)
 	add_pending_object(revs, obj, "HEAD");
 }
 
-int cmd_diff(int argc, const char **argv, char **envp)
+int cmd_diff(int argc, const char **argv, const char *prefix)
 {
 	int i;
 	struct rev_info rev;
@@ -251,7 +251,7 @@ int cmd_diff(int argc, const char **argv, char **envp)
 	 */
 
 	git_config(git_diff_ui_config);
-	init_revisions(&rev);
+	init_revisions(&rev, prefix);
 
 	argc = setup_revisions(argc, argv, &rev, NULL);
 	if (!rev.diffopt.output_format) {
@@ -346,7 +346,15 @@ int cmd_diff(int argc, const char **argv, char **envp)
 		return builtin_diff_index(&rev, argc, argv);
 	else if (ents == 2)
 		return builtin_diff_tree(&rev, argc, argv, ent);
+	else if ((ents == 3) && (ent[0].item->flags & UNINTERESTING)) {
+		/* diff A...B where there is one sane merge base between
+		 * A and B.  We have ent[0] == merge-base, ent[1] == A,
+		 * and ent[2] == B.  Show diff between the base and B.
+		 */
+		return builtin_diff_tree(&rev, argc, argv, ent);
+	}
 	else
-		return builtin_diff_combined(&rev, argc, argv, ent, ents);
+		return builtin_diff_combined(&rev, argc, argv,
+					     ent, ents);
 	usage(builtin_diff_usage);
 }