hideablerevs: expand docstring to warn about possible traps
Sean Farley just wasted multiple hours trying to figure out why his code was
crashing. We update the docstring to make the constraint clearer.
$ cat > unix2mac.py <<EOF
> import sys
>
> for path in sys.argv[1:]:
> data = file(path, 'rb').read()
> data = data.replace('\n', '\r')
> file(path, 'wb').write(data)
> EOF
$ cat > print.py <<EOF
> import sys
> print(sys.stdin.read().replace('\n', '<LF>').replace('\r', '<CR>').replace('\0', '<NUL>'))
> 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
[255]
$ hg cat f | python print.py
hello<LF>
$ cat f | python print.py
hello<CR>