[MERGE] Config.get_user_section() API

[Ian Clatworthy]

Robert Collins wrote:

> What is it in aid of - you say its for enhanced hooks, but any hook can
> already ask for the appropriate config (branch/tree/location/user) and
> work with that.

It's for the hooks infrastructure to load the set of user-configured (as
opposed to plugin configured) hooks. So the idea is that a user can have
settings like this:

[pre-export-hooks]
docs = make docs

[post-commit-message-hooks]
validate = checkCommitMsg.sh

Those settings may be found in any of the config files and ought to be
combined sensibly using the normal precedence rules.

FWIW, Jelmer gets around this in his shell-hook plugin by only
supporting a single script per hook and only looking in branch.conf, e.g.

[hooks]
pre-export = make docs
post-commit-message = checkCommitMsg.sh

That is better than what we currently have ('write a plugin') but it
doesn't scale. As explained in http://bazaar-vcs.org/BzrHooks, Hg gets
around this by using an optional tagging syntax:

[hooks]
pre-export = make docs
pre-export.foo = make foo

I don't like that - I much prefer the way I'm proposing. Either way, a
get_user_section() API is needed to find the complete set of hooks.

The API is also extremely useful within a given hook or plugin. If I'm
writing an ACL hook say, there's every chance I'll want to do something
like this to get the configuration settings:

  settings = cfg.get_user_section('acl-settings')

It's true that plugins can create and use their own config files but
there are times when reusing the standard config infrastructure by
adding new sections works better.

Ian C.