scm interface

[ct]

abstract the libgit.lua to a generic scm interface and implement

_sys/scm/git
_sys/scm/plain

... like modules

then introduce a _scm metadata which records which scm actually is used for a given subtree.

[ct]

Replying to ct:

abstract the libgit.lua to a generic scm interface

Brainstorming, what interfaces are needed:

1. commit a single file
2. revert (remove) a commit in case of spam
3. get the history of a whole repository (RecentChanges)
4. get a scm-specific identifier of a given file revision (some string), needed for 5.
5. perform a three way merge in case of concurrent edits, let the user fix conflicts