commit: add repository argument to get_cached_commit_buffer

Add a repository argument to allow callers of get_cached_commit_buffer to
be more specific about which repository to handle. This is a small
mechanical change; it doesn't change the implementation to handle
repositories other than the_repository yet.

As with the previous commits, use a macro to catch callers passing a
repository other than the_repository at compile time.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/pretty.c b/pretty.c
index cbd25b6..cde4fe0 100644
--- a/pretty.c
+++ b/pretty.c
@@ -630,7 +630,7 @@ const char *logmsg_reencode(const struct commit *commit,
 		 * the cached copy from get_commit_buffer, we need to duplicate it
 		 * to avoid munging the cached copy.
 		 */
-		if (msg == get_cached_commit_buffer(commit, NULL))
+		if (msg == get_cached_commit_buffer(the_repository, commit, NULL))
 			out = xstrdup(msg);
 		else
 			out = (char *)msg;