refactor utils

[ilgooz]

i see that we have quite a lot utils.go, utils package inside the project. i think we should reduce them and serve under a root level utils package as possible but use different package names for each different util under utils/ e.g.:

util/
  gitutil/ > gitutil.Clone()

lets also give a second check to this article about package namings: https://blog.golang.org/package-names

related with this comment.

[krhubert]

I propose struct like here:

https://github.com/krhubert/gox

We have already xpflag in our repo. Maybe add x/ directory under repo root:

x/
  xgit/
  xpflag/
  x....

util can be used for things that won't fit into any extensions (or totally different purpose)...

[ilgooz]

i like the name x instead using util but is there any meaning of x anyway?

[krhubert]

yep x stands for eXtension and it's there to not get the same name for 2 pkgs (also importing git pkg into git pkg - or any other pkg name - can lead to ugly/error-prone code). I preffer x over util only because is shorter.

[ilgooz]

i like the x name but i also like to stay package agnostic while naming x packages. in this context xgit should be getting its name because it's related with Git, not for extending a feature of github.com/src-d/go-git. this way we can also put generic utils under x package without worrying about if its name fits with a existing package.