GitConfigParser.set_value should support setting multiple values for an option

[craftyguy]

GitConfigParser.set_value does not allow for setting multiple values for a given option.
One example of this is in the refspec documentation for git:

remote "origin"]
	url = https://github.com/schacon/simplegit-progit
	fetch = +refs/heads/master:refs/remotes/origin/master
	fetch = +refs/heads/experiment:refs/remotes/origin/experiment

If you try to call set_value twice with the two different refspecs above, only the last one will get set.. which makes sense since set_value seems to only support setting one value for a given option.

[ajdavis]

I can make a pull request for this, are the maintainers interested?

[Byron]

@ajdavis Yes, I am absolutely interested. The implementation will certainly require some effort. In order not to break the existing API, it might be easiest to add methods specifically for getting and setting multiple values.

[maiamcc]

FWIW, tangential to this ticket but I'd also appreciate it if there were a way to GET multiple values for a given option (equivalent to git config --get-all). Should I open a new issue?

[Byron]

By now this is implemented thanks to a generous PR.