Introduce new pretty formats %g[sdD] for reflog information

Add three new --pretty=format escapes:

  %gD  long  reflog descriptor (e.g. refs/stash@{0})
  %gd  short reflog descriptor (e.g. stash@{0})
  %gs  reflog message

This is achieved by passing down the reflog info, if any, inside the
pretty_print_context struct.

We use the newly refactored get_reflog_selector(), and give it some
extra functionality to extract a shortened ref.  The shortening is
cached inside the commit_reflogs struct; the only allocation of it
happens in read_complete_reflog(), where it is initialised to 0.  Also
add another helper get_reflog_message() for the message extraction.

Note that the --format="%h %gD: %gs" tests may not work in real
repositories, as the --pretty formatter doesn't know to leave away the
": " on the last commit in an incomplete (because git-gc removed the
old part) reflog.  This equivalence is nevertheless the main goal of
this patch.

Thanks to Jeff King for reviews, the %gd testcase and documentation.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/pretty.c b/pretty.c
index d6d57ebd2..fc65fca58 100644
--- a/pretty.c
+++ b/pretty.c
@@ -7,6 +7,7 @@
 #include "mailmap.h"
 #include "log-tree.h"
 #include "color.h"
+#include "reflog-walk.h"
 
 static char *user_format;
 
@@ -701,6 +702,22 @@ static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
 	case 'd':
 		format_decoration(sb, commit);
 		return 1;
+	case 'g':		/* reflog info */
+		switch(placeholder[1]) {
+		case 'd':	/* reflog selector */
+		case 'D':
+			if (c->pretty_ctx->reflog_info)
+				get_reflog_selector(sb,
+						    c->pretty_ctx->reflog_info,
+						    c->pretty_ctx->date_mode,
+						    (placeholder[1] == 'd'));
+			return 2;
+		case 's':	/* reflog message */
+			if (c->pretty_ctx->reflog_info)
+				get_reflog_message(sb, c->pretty_ctx->reflog_info);
+			return 2;
+		}
+		return 0;	/* unknown %g placeholder */
 	}
 
 	/* For the rest we have to parse the commit header. */