diff --git a/Documentation/git-diff-cache.txt b/Documentation/git-diff-cache.txt
index 9c7832f6e2..14041f3df8 100644
--- a/Documentation/git-diff-cache.txt
+++ b/Documentation/git-diff-cache.txt
@@ -57,7 +57,8 @@ OPTIONS
 	<orderfile>, which has one shell glob pattern per line.
 
 -R::
-	Output diff in reverse.
+	Swap two inputs; that is, show differences from cache or
+	on-disk file to tree contents.
 
 --cached::
 	do not consider the on-disk file at all
diff --git a/Documentation/git-diff-files.txt b/Documentation/git-diff-files.txt
index 8439355b06..58137b3b9e 100644
--- a/Documentation/git-diff-files.txt
+++ b/Documentation/git-diff-files.txt
@@ -27,7 +27,8 @@ OPTIONS
 	Remain silent even on nonexisting files
 
 -R::
-	Output diff in reverse.
+	Swap two inputs; that is, show differences from on-disk files
+	to cache contents.
 
 -B::
 	Break complete rewrite changes into pairs of delete and create.
diff --git a/Documentation/git-diff-helper.txt b/Documentation/git-diff-helper.txt
index 90342c9125..29c5967d13 100644
--- a/Documentation/git-diff-helper.txt
+++ b/Documentation/git-diff-helper.txt
@@ -9,7 +9,7 @@ git-diff-helper - Generates patch format output for git-diff-*
 
 SYNOPSIS
 --------
-'git-diff-helper' [-z] [-S<string>]
+'git-diff-helper' [-z] [-S<string>] [-O<orderfile>]
 
 DESCRIPTION
 -----------
@@ -24,6 +24,9 @@ OPTIONS
 -S<string>::
 	Look for differences that contains the change in <string>.
 
+-O<orderfile>::
+	Output the patch in the order specified in the
+	<orderfile>, which has one shell glob pattern per line.
 
 See Also
 --------
diff --git a/Documentation/git-diff-tree.txt b/Documentation/git-diff-tree.txt
index 9e038856e3..762546bfe9 100644
--- a/Documentation/git-diff-tree.txt
+++ b/Documentation/git-diff-tree.txt
@@ -43,7 +43,7 @@ OPTIONS
 	Detect copies as well as renames.
 
 -R::
-	Output diff in reverse.
+	Swap two input trees.
 
 -S<string>::
 	Look for differences that contains the change in <string>.
diff --git a/diff-cache.c b/diff-cache.c
index 2aaf16a39d..8e5f72bf3f 100644
--- a/diff-cache.c
+++ b/diff-cache.c
@@ -157,7 +157,7 @@ static void mark_merge_entries(void)
 }
 
 static char *diff_cache_usage =
-"git-diff-cache [-p] [-r] [-z] [-m] [-M] [-C] [-R] [-S<string>] [--cached] <tree-ish> [<path>...]";
+"git-diff-cache [-p] [-r] [-z] [-m] [-M] [-C] [-R] [-S<string>] [-O<orderfile>] [--cached] <tree-ish> [<path>...]";
 
 int main(int argc, const char **argv)
 {
diff --git a/diff-files.c b/diff-files.c
index 3b05497a85..a425112c9e 100644
--- a/diff-files.c
+++ b/diff-files.c
@@ -7,7 +7,7 @@
 #include "diff.h"
 
 static const char *diff_files_usage =
-"git-diff-files [-p] [-q] [-r] [-z] [-M] [-C] [-R] [-S<string>] [paths...]";
+"git-diff-files [-p] [-q] [-r] [-z] [-M] [-C] [-R] [-S<string>] [-O<orderfile>] [paths...]";
 
 static int diff_output_format = DIFF_FORMAT_HUMAN;
 static int detect_rename = 0;
diff --git a/diff-helper.c b/diff-helper.c
index c9e287f652..04e6f2cd72 100644
--- a/diff-helper.c
+++ b/diff-helper.c
@@ -7,11 +7,22 @@
 
 static const char *pickaxe = NULL;
 static int pickaxe_opts = 0;
+static const char *orderfile = NULL;
 static int line_termination = '\n';
 static int inter_name_termination = '\t';
 
+static void flush_them(int ac, const char **av)
+{
+	diffcore_std(av + 1,
+		     0, 0, /* no renames */
+		     pickaxe, pickaxe_opts,
+		     -1, /* no breaks */
+		     orderfile);
+	diff_flush(DIFF_FORMAT_PATCH, 0);
+}
+
 static const char *diff_helper_usage =
-	"git-diff-helper [-z] [-S<string>] paths...";
+	"git-diff-helper [-z] [-S<string>] [-O<orderfile>] paths...";
 
 int main(int ac, const char **av) {
 	struct strbuf sb;
@@ -131,17 +142,9 @@ int main(int ac, const char **av) {
 					  new_path);
 			continue;
 		}
-		if (1 < ac)
-			diffcore_pathspec(av + 1);
-		if (pickaxe)
-			diffcore_pickaxe(pickaxe, pickaxe_opts);
-		diff_flush(DIFF_FORMAT_PATCH, 0);
+		flush_them(ac, av);
 		printf(garbage_flush_format, sb.buf);
 	}
-	if (1 < ac)
-		diffcore_pathspec(av + 1);
-	if (pickaxe)
-		diffcore_pickaxe(pickaxe, pickaxe_opts);
-	diff_flush(DIFF_FORMAT_PATCH, 0);
+	flush_them(ac, av);
 	return 0;
 }
diff --git a/diff-tree.c b/diff-tree.c
index a6d358fb34..c3a5617c57 100644
--- a/diff-tree.c
+++ b/diff-tree.c
@@ -397,7 +397,7 @@ static int diff_tree_stdin(char *line)
 }
 
 static char *diff_tree_usage =
-"git-diff-tree [-p] [-r] [-z] [--stdin] [-M] [-C] [-R] [-S<string>] [-m] [-s] [-v] [-t] <tree-ish> <tree-ish>";
+"git-diff-tree [-p] [-r] [-z] [--stdin] [-M] [-C] [-R] [-S<string>] [-O<orderfile>] [-m] [-s] [-v] [-t] <tree-ish> <tree-ish>";
 
 int main(int argc, const char **argv)
 {
diff --git a/diff.h b/diff.h
index 3fcf7010e3..c64880cdb1 100644
--- a/diff.h
+++ b/diff.h
@@ -35,21 +35,13 @@ extern int diff_scoreopt_parse(const char *opt);
 #define DIFF_SETUP_REVERSE      	1
 #define DIFF_SETUP_USE_CACHE		2
 #define DIFF_SETUP_USE_SIZE_CACHE	4
+
 extern void diff_setup(int flags);
 
 #define DIFF_DETECT_RENAME	1
 #define DIFF_DETECT_COPY	2
 
-extern void diffcore_rename(int rename_copy, int minimum_score);
-
 #define DIFF_PICKAXE_ALL	1
-extern void diffcore_pickaxe(const char *needle, int opts);
-
-extern void diffcore_pathspec(const char **pathspec);
-
-extern void diffcore_order(const char *orderfile);
-
-extern void diffcore_break(int max_score);
 
 extern void diffcore_std(const char **paths,
 			 int detect_rename, int rename_score,
diff --git a/diffcore.h b/diffcore.h
index 1f4b32c1c1..2e613ebe89 100644
--- a/diffcore.h
+++ b/diffcore.h
@@ -73,6 +73,12 @@ extern struct diff_filepair *diff_queue(struct diff_queue_struct *,
 					struct diff_filespec *);
 extern void diff_q(struct diff_queue_struct *, struct diff_filepair *);
 
+extern void diffcore_pathspec(const char **pathspec);
+extern void diffcore_break(int);
+extern void diffcore_rename(int rename_copy, int);
+extern void diffcore_pickaxe(const char *needle, int opts);
+extern void diffcore_order(const char *orderfile);
+
 #define DIFF_DEBUG 0
 #if DIFF_DEBUG
 void diff_debug_filespec(struct diff_filespec *, int, const char *);