GetComponents: add support to set push_url in git

[Roland Haas]

this lets us check out using the anonymous URL but push using the authenticated URL

this in turn is useful for thornlist where users only have push rights to some repos but not all of them so --no-anonymous does not work well for them

[Roland Haas]

Pull request is here: https://github.com/gridaphobe/CRL/pull/14

[Roland Haas]

Please review

[Roland Haas]

@Steven R. Brandt says (in ET call): please apply.

[Roland Haas]

Applied as git hash 5a0c93b "GetComponents: add support to set push_url in git" of CRL

[Roland Haas]

Thank you.