Add git for versioning (via 'hook' in the config)

[robertbeal]

Also added in using apk's virtual "group" dependencies for cleaner dependencies.

Git (although it could be anything) is an easy way to do versioning as per the radicale instructions: http://radicale.org/versioning/

Hope it all looks ok. Great image btw.

[tomsquest]

Hi Robert,

Thanks a lot for your PR:

• Convenient to have a more complete image
• I learnt about virtual dependencies in Alpine

About your PR, I saw another commit about adding openssh-client but I do not see in your PR. Is it still required ?

[tomsquest]

@robertbeal can you confirm about openssh-client ?

[robertbeal]

Hey sorry, just back from holiday. Ah yeah I played around with putting openssh in but reverted the commit (and squashed it).

I was thinking about adding a "push" to the hook (hence wanting an ssh client), but in the end decided it was better to do so outside of radicale.

[tomsquest]

Thanks @robertbeal