[RFC PATCH 4/4] range-diff: add section headers to the outer hunk header

[Thomas Gummerer <t.gummerer@gmail.com>]

Add the section headers we introduced in the previous commit to the
outer diff's hunk headers.  This makes it easier to understand which
change we are actually looking at.  For example an outer hunk header
might now look like:

    @@ -77,15 +78,43 @@ modified file Documentation/config/interactive.txt

while previously it would have only been

    @@ -77,15 +78,43 @@

which doesn't give a lot of context for the change that follows.

For completeness also add section headers for the commit metadata and
the commit message, although they are arguably less important.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
---
 range-diff.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/range-diff.c b/range-diff.c
index aa466060ef..15ac54f369 100644
--- a/range-diff.c
+++ b/range-diff.c
@@ -124,8 +124,10 @@ static int read_patches(const char *range, struct string_list *list)
 			strbuf_addstr(&buf, " ##\n");
 		} else if (in_header) {
 			if (starts_with(line.buf, "Author: ")) {
+				strbuf_addstr(&buf, " ## Metadata ##\n");
 				strbuf_addbuf(&buf, &line);
 				strbuf_addstr(&buf, "\n\n");
+				strbuf_addstr(&buf, " ## Commit message ##\n");
 			} else if (starts_with(line.buf, "    ")) {
 				strbuf_rtrim(&line);
 				strbuf_addbuf(&buf, &line);
@@ -387,8 +389,8 @@ static void output_pair_header(struct diff_options *diffopt,
 	fwrite(buf->buf, buf->len, 1, diffopt->file);
 }
 
-static struct userdiff_driver no_func_name = {
-	.funcname = { "$^", 0 }
+static struct userdiff_driver section_headers = {
+	.funcname = { "^ ## (.*) ##$", REG_EXTENDED }
 };
 
 static struct diff_filespec *get_filespec(const char *name, const char *p)
@@ -400,7 +402,7 @@ 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;
+	spec->driver = &section_headers;
 
 	return spec;
 }
-- 
2.21.0.593.g511ec345e1