Add mirror option for git cloning

[Strech]

Example:

vcsrepo { '/path/to/repo':
  ensure   => mirror,
  provider => git,
  source   => 'git://example.com/repo.git',
}

[sodabrew]

This looks good, and thank you very much for writing both unit tests and README text! Past PRs to provide mirror support were #233 and #267 (links for "SEO" not because you need to pull older code from them.

Nit pick: could you avoid changing so much whitespace in the README? It would be OK to have a whitespace-only commit to correct the whitespace before adding your new section, but having it mixed in makes a harder to read diff.

[sodabrew]

As for behavior of the mirror, should it behave like "latest" and always fetch the remote on every puppet run?

[Strech]

As for behavior of the mirror, should it behave like "latest" and always fetch the remote on every puppet run?

Nope, mirror is mostly like bare, it will copy everything as bare do, but plus refs
http://stackoverflow.com/questions/3959924/whats-the-difference-between-git-clone-mirror-and-git-clone-bare

[Strech]

@sodabrew I reduce changes in README (sorry for massive whitespace cleanup 😿 )

[Strech]

@sodabrew Hi, can you have a look at this PR? Is everything ok?

[bmjen]

This looks good @Strech ! Thanks for the contribution!