hooks: forbid ':' in hook name...
hooks: forbid ':' in hook name
The `:` character is a special separator in the config and it seems same do to
the same for hooks. This is necessary to improve the experience around the
HGPLAIN behavior change in 5.7. See next changesets for details.
Differential Revision:
https://phab.mercurial-scm.org/D9978