Feature/rev parse command

Implement the rev-parse command

Based on the work of @John-Schlick (#48) & @matteosister (John-Schlick-RevParse branch)

previous work is completed with more integration with Branch & Object and more tests. 

please tell me what should be improved before this PR can be merge. I don't know much about the rev-parse command we essentially need it for the --is-bare-repository so I don't know what other meaningful tests I can add


regards