prune-packed: only show progress when stderr is a tty

diff --git a/builtin-mailinfo.c b/builtin-mailinfo.c
index d498b1cd2d9a2a99bd9564615dfe9bc98ecca47f..c90cd312ac99fe9a2169664e86a089b5378cacbe 100644 (file)
--- a/builtin-mailinfo.c
+++ b/builtin-mailinfo.c
@@ -785,8 +785,10 @@ static int handle_commit_msg(struct strbuf *line)
 
        if (use_scissors && is_scissors_line(line)) {
                int i;
-               rewind(cmitmsg);
-               ftruncate(fileno(cmitmsg), 0);
+               if (fseek(cmitmsg, 0L, SEEK_SET))
+                       die_errno("Could not rewind output message file");
+               if (ftruncate(fileno(cmitmsg), 0))
+                       die_errno("Could not truncate output message file at scissors");
                still_looking = 1;
 
                /*