errors: use exit code 40 for when a hook fails
A hook can be used for checking inputs, state, configuration,
security, etc., so it's unclear which of the existing exit codes to
use. Let's instead add one specifically for failed hooks. I picked 40.
Differential Revision: https://phab.mercurial-scm.org/D9910
$ cat > unix2mac.py <<EOF
> import sys
>
> for path in sys.argv[1:]:
> data = open(path, 'rb').read()
> data = data.replace(b'\n', b'\r')
> open(path, 'wb').write(data)
> EOF
$ hg init
$ echo '[hooks]' >> .hg/hgrc
$ echo 'pretxncommit.cr = python:hgext.win32text.forbidcr' >> .hg/hgrc
$ echo 'pretxnchangegroup.cr = python:hgext.win32text.forbidcr' >> .hg/hgrc
$ cat .hg/hgrc
[hooks]
pretxncommit.cr = python:hgext.win32text.forbidcr
pretxnchangegroup.cr = python:hgext.win32text.forbidcr
$ echo hello > f
$ hg add f
$ hg ci -m 1
$ "$PYTHON" unix2mac.py f
$ hg ci -m 2
attempt to commit or push text file(s) using CR line endings
in dea860dc51ec: f
transaction abort!
rollback completed
abort: pretxncommit.cr hook failed
[40]
$ hg cat f | f --hexdump
0000: 68 65 6c 6c 6f 0a |hello.|
$ f --hexdump f
f:
0000: 68 65 6c 6c 6f 0d |hello.|