[MERGE][RFC] Enhanced hooks

[Ian Clatworthy]

Robert Collins wrote:

> This needs discussion, urgently I think. We /had/ hooks like this and
> decided it was a pretty crappy UI and stopped. Why are we bringing it
> back ?

Our current way of configuring hooks leaves a lot to be desired: it
requires 'writing a plugin'. Other systems are easier and potential
adopters have rejected Bazaar on this point alone. See
https://lists.ubuntu.com/archives/bazaar/2007q4/032657.html.

Following that feedback, I kicked off a discussion thread on this topic
asking people for what they wanted:
https://lists.ubuntu.com/archives/bazaar/2007q4/035833.html. Shell hooks
was repeated time and time again.

Jelmer recently announced his shell-hook plugin. He and I both believe
that the functionality needs to be in the core. The patches submitted
yesterday add that.

The question will then arise, "If shell hooks can be configured in a
flexible way, why can't Python hooks?".

Ian C.