files_for_each_reflog_ent_reverse(): close stream and free strbuf on error

Exit the loop orderly through the cleanup code, instead of dashing out
with logfp still open and sb leaking.

Found with Cppcheck.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Reviewed-by: Jeff King <peff@peff.net>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs/files-backend.c

@@ -3169,8 +3169,8 @@ static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
 
 	/* Jump to the end */
 	if (fseek(logfp, 0, SEEK_END) < 0)
-		return error("cannot seek back reflog for %s: %s",
-			     refname, strerror(errno));
+		ret = error("cannot seek back reflog for %s: %s",
+			    refname, strerror(errno));
 	pos = ftell(logfp);
 	while (!ret && 0 < pos) {
 		int cnt;
@@ -3180,13 +3180,17 @@ static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
 
 		/* Fill next block from the end */
 		cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
-		if (fseek(logfp, pos - cnt, SEEK_SET))
-			return error("cannot seek back reflog for %s: %s",
-				     refname, strerror(errno));
+		if (fseek(logfp, pos - cnt, SEEK_SET)) {
+			ret = error("cannot seek back reflog for %s: %s",
+				    refname, strerror(errno));
+			break;
+		}
 		nread = fread(buf, cnt, 1, logfp);
-		if (nread != 1)
-			return error("cannot read %d bytes from reflog for %s: %s",
-				     cnt, refname, strerror(errno));
+		if (nread != 1) {
+			ret = error("cannot read %d bytes from reflog for %s: %s",
+				    cnt, refname, strerror(errno));
+			break;
+		}
 		pos -= cnt;
 
 		scanp = endp = buf + cnt;