The regex in r245683 is
match = re.search('^+++\ "?(.?/){%s}([^ \t\"])' % args.p, line)
while the regex in your e-mail was
match = re.search('^+++\ "?(.?/){%s}([^ \t\"\n])' % args.p, line)

there are three changes between the regexs.

1. The additional \n I understand.
2. , + are not escaped which I do not understand why as + is a special character in Python regex (see https://docs.python.org/2/library/re.html).
3. The star after [^ \t\"\n] went missing.

I've committed 1), additional \n on r246575. I hope this is enough to fix the issue but without an example cannot test this.
If more changes are needed please reopen the bug with a short example diff that breaks the regex so I can test everything before committing.