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, 32 insertions, 3 deletions

diff --git a/reflog-walk.c b/reflog-walk.c
index 596bafebdd..caba4f743f 100644
--- a/reflog-walk.c
+++ b/reflog-walk.c
@@ -8,6 +8,7 @@
 
 struct complete_reflogs {
 	char *ref;
+	const char *short_ref;
 	struct reflog_info {
 		unsigned char osha1[20], nsha1[20];
 		char *email;
@@ -243,15 +244,26 @@ void fake_reflog_parent(struct reflog_walk_info *info, struct commit *commit)
 
 void get_reflog_selector(struct strbuf *sb,
 			 struct reflog_walk_info *reflog_info,
-			 enum date_mode dmode)
+			 enum date_mode dmode,
+			 int shorten)
 {
 	struct commit_reflog *commit_reflog = reflog_info->last_commit_reflog;
 	struct reflog_info *info;
+	const char *printed_ref;
 
 	if (!commit_reflog)
 		return;
 
-	strbuf_addf(sb, "%s@{", commit_reflog->reflogs->ref);
+	if (shorten) {
+		if (!commit_reflog->reflogs->short_ref)
+			commit_reflog->reflogs->short_ref
+				= shorten_unambiguous_ref(commit_reflog->reflogs->ref, 0);
+		printed_ref = commit_reflog->reflogs->short_ref;
+	} else {
+		printed_ref = commit_reflog->reflogs->ref;
+	}
+
+	strbuf_addf(sb, "%s@{", printed_ref);
 	if (commit_reflog->flag || dmode) {
 		info = &commit_reflog->reflogs->items[commit_reflog->recno+1];
 		strbuf_addstr(sb, show_date(info->timestamp, info->tz, dmode));
@@ -263,6 +275,23 @@ void get_reflog_selector(struct strbuf *sb,
 	strbuf_addch(sb, '}');
 }
 
+void get_reflog_message(struct strbuf *sb,
+			struct reflog_walk_info *reflog_info)
+{
+	struct commit_reflog *commit_reflog = reflog_info->last_commit_reflog;
+	struct reflog_info *info;
+	size_t len;
+
+	if (!commit_reflog)
+		return;
+
+	info = &commit_reflog->reflogs->items[commit_reflog->recno+1];
+	len = strlen(info->message);
+	if (len > 0)
+		len--; /* strip away trailing newline */
+	strbuf_add(sb, info->message, len);
+}
+
 void show_reflog_message(struct reflog_walk_info *reflog_info, int oneline,
 	enum date_mode dmode)
 {
@@ -272,7 +301,7 @@ void show_reflog_message(struct reflog_walk_info *reflog_info, int oneline,
 		struct strbuf selector = STRBUF_INIT;
 
 		info = &commit_reflog->reflogs->items[commit_reflog->recno+1];
-		get_reflog_selector(&selector, reflog_info, dmode);
+		get_reflog_selector(&selector, reflog_info, dmode, 0);
 		if (oneline) {
 			printf("%s: %s", selector.buf, info->message);
 		}