RFR: cli: add git-proxy tool

[Robin Westberg]

On Thu, 16 Apr 2020 11:57:39 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that adds a small new tool: `git-proxy`. `git-proxy`
> can be used to set up the `HTTPS_PROXY` and `HTTP_PROXY` environment
> variables based on either the `http.proxy` configuration setting or the `-c
> http.proxy=` argument. Finally `git-proxy` will also set up the
> `GIT_SSH_COMMAND` environment variable to use the `CONNECT` method for tunneling
> SSH over an HTTP proxy.
> 
> Testing:
> - manual testing of `git-proxy`
> - `make test` passes on Linux x64
> 
> Thanks,
> Erik

Looks good!

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/585