[PATCH/RFC] pretty.c: add %O format specifier to format_commit_one()

[Alexander Shishkin <ash@koowaldah.org>]

This specifier represents the number of each commit in the output
stream.

Signed-off-by: Alexander Shishkin <ash@koowaldah.org>
---
 Documentation/pretty-formats.txt |    3 ++-
 pretty.c                         |    5 +++++
 2 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 1686a54..7b0cab1 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -137,7 +137,8 @@ The placeholders are:
 - '%%': a raw '%'
 - '%x00': print a byte from a hex code
 - '%w([<w>[,<i1>[,<i2>]]])': switch line wrapping, like the -w option of
-  linkgit:git-shortlog[1].
+  linkgit:git-shortlog[1]
+- '%O': number of the record in the output.
 
 NOTE: Some placeholders may depend on other options given to the
 revision traversal engine. For example, the `%g*` reflog options will
diff --git a/pretty.c b/pretty.c
index 7cb3a2a..3e3d399 100644
--- a/pretty.c
+++ b/pretty.c
@@ -11,6 +11,7 @@
 #include "reflog-walk.h"
 
 static char *user_format;
+static int record_number;
 
 static void save_user_format(struct rev_info *rev, const char *cp, int is_tformat)
 {
@@ -639,6 +640,9 @@ static size_t format_commit_one(struct strbuf *sb, const char *placeholder,
 
 	/* these are independent of the commit */
 	switch (placeholder[0]) {
+	case 'O':
+		strbuf_addf(sb, "%d", record_number);
+		return 1;
 	case 'C':
 		if (placeholder[1] == '(') {
 			const char *end = strchr(placeholder + 2, ')');
@@ -899,6 +903,7 @@ void format_commit_message(const struct commit *commit,
 	context.wrap_start = sb->len;
 	strbuf_expand(sb, format, format_commit_item, &context);
 	rewrap_message_tail(sb, &context, 0, 0, 0);
+	record_number++;
 }
 
 static void pp_header(enum cmit_fmt fmt,
-- 
1.7.0.4