Import existing hook script when installing

[klauern]

I use awslabs/git-secrets as a pre-install hook for all Git clone operations, and I would like to maintain having that when using Lefthook. In looking how lefthook install works, it won't take the existing hooks and import it, and I'm not sure how to enable a global set of hooks that will be run.

I'd prefer if there were an option to not replace my .git/hooks with lefthook's, and instead append the lefthook configuration. Barring that, I'd like to see some options for global hooks that could be installed or set up once in your $HOME/.lefthook dir, so it could be included by default for all lefthook operations.

[Arkweid]

It sound very close to shared configs #30

[Arkweid]

Done https://github.com/Arkweid/lefthook/blob/master/docs/full_guide.md#extends-option