check-attr and check-ignore have the potential to deadlock callers
which do not read back the output in real-time. For example, if a
caller writes N paths out and then reads N lines back in, it risks
becoming blocked on write() to check-*, and check-* is blocked on
write back to the caller. Somebody has to buffer; the pipe buffers
provide some leeway, but they are limited.
Thanks to Peff for pointing this out:
http://article.gmane.org/gmane.comp.version-control.git/220534
Signed-off-by: Adam Spiers <git@adamspiers.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If `-n` or `--non-matching` are specified, non-matching pathnames will
also be output, in which case all fields in each output record except
for <pathname> will be empty. This can be useful when running
check-ignore as a background process, so that files can be
incrementally streamed to STDIN, and for each of these files, STDOUT
will indicate whether that file matched a pattern or not. (Without
this option, it would be impossible to tell whether the absence of
output for a given file meant that it didn't match any pattern, or
that the result simply hadn't been flushed to STDOUT yet.)
Signed-off-by: Adam Spiers <git@adamspiers.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
