log_ref_write_1(): don't depend on logfile argument

It's unnecessary to pass a strbuf holding the reflog path up and down
the call stack now that it is hardly needed by the callers. Remove the
places where log_ref_write_1() uses it, in preparation for making it
internal to log_ref_setup().

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs/files-backend.c

@@ -2838,14 +2838,18 @@ static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
 	result = log_ref_write_fd(logfd, old_sha1, new_sha1,
 				  git_committer_info(0), msg);
 	if (result) {
-		strbuf_addf(err, "unable to append to '%s': %s", logfile->buf,
+		int save_errno = errno;
-			    strerror(errno));
+
+		strbuf_addf(err, "unable to append to '%s': %s",
+			    git_path("logs/%s", refname), strerror(save_errno));
 		close(logfd);
 		return -1;
 	}
 	if (close(logfd)) {
-		strbuf_addf(err, "unable to append to '%s': %s", logfile->buf,
+		int save_errno = errno;
-			    strerror(errno));
+
+		strbuf_addf(err, "unable to append to '%s': %s",
+			    git_path("logs/%s", refname), strerror(save_errno));
 		return -1;
 	}
 	return 0;