[go-borges] Change arguments to specify libraries

[jfontan]

To pass directories with repos --directory will be used. By default it will add non bare git repositories but this can be changed with:

--format (siva|git)
--bare false
--rooted true
--bucket 2

• git format can specify if they are bare or not.
• siva format cam specify bucketing level and if it's rooted or not

Defaults are the ones in the example. Next version will use auto discovery of bareness.