range-diff: do not show "function names" in hunk headers

We are comparing complete, formatted commit messages with patches. There
are no function names here, so stop looking for them.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

range-diff.c

@@ -9,6 +9,7 @@
 #include "diffcore.h"
 #include "commit.h"
 #include "pretty.h"
+#include "userdiff.h"
 
 struct patch_util {
 	/* For the search for an exact match */
@@ -302,6 +303,10 @@ static void output_pair_header(struct strbuf *buf,
 	fwrite(buf->buf, buf->len, 1, stdout);
 }
 
+static struct userdiff_driver no_func_name = {
+	.funcname = { "$^", 0 }
+};
+
 static struct diff_filespec *get_filespec(const char *name, const char *p)
 {
 	struct diff_filespec *spec = alloc_filespec(name);
@@ -311,6 +316,7 @@ static struct diff_filespec *get_filespec(const char *name, const char *p)
 	spec->size = strlen(p);
 	spec->should_munmap = 0;
 	spec->is_stdin = 1;
+	spec->driver = &no_func_name;
 
 	return spec;
 }