fast-import.c: don't try to commit marks file if write failed

We also move the assignment of -1 to the lock file descriptor
up, so that rollback_lock_file() can be called safely after a
possible attempt to fclose(). This matches the contents of
the 'if' statement just above testing success of fdopen().
Signed-off-by: NBrandon Casey <casey@nrlssc.navy.mil>
Acked-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

fast-import.c

@@ -1545,19 +1545,27 @@ static void dump_marks(void)
 		return;
 	}
 
-	dump_marks_helper(f, 0, marks);
-	if (ferror(f) || fclose(f))
-		failure |= error("Unable to write marks file %s: %s",
-			mark_file, strerror(errno));
 	/*
-	 * Since the lock file was fdopen()'ed and then fclose()'ed above,
-	 * assign -1 to the lock file descriptor so that commit_lock_file()
+	 * Since the lock file was fdopen()'ed, it should not be close()'ed.
+	 * Assign -1 to the lock file descriptor so that commit_lock_file()
 	 * won't try to close() it.
 	 */
 	mark_lock.fd = -1;
-	if (commit_lock_file(&mark_lock))
-		failure |= error("Unable to write commit file %s: %s",
+
+	dump_marks_helper(f, 0, marks);
+	if (ferror(f) || fclose(f)) {
+		rollback_lock_file(&mark_lock);
+		failure |= error("Unable to write marks file %s: %s",
 			mark_file, strerror(errno));
+		return;
+	}
+
+	if (commit_lock_file(&mark_lock)) {
+		rollback_lock_file(&mark_lock);
+		failure |= error("Unable to commit marks file %s: %s",
+			mark_file, strerror(errno));
+		return;
+	}
 }
 
 static int read_next_command(void)