Separate command line options from arguments with a double dash

### What feature do you want to see added?

https://www.gnu.org/software/bash/manual/html_node/Shell-Builtin-Commands.html says that "--" is used to clearly show the end of options. Extend the git client plugin calls to command line git to consistently use "--" to show the end of options

### Upstream changes

_No response_

### Are you interested in contributing this feature?

Possibly interested. The test cases to exercise the change will be very interesting.

Start by locating the git-client-plugin calls that invoke command-line Git and review the existing test cases for those calls. The work is done when relevant option and argument boundaries consistently use "--" and the tests cover the changed behavior and pass.

Written by the indexing model from the issue text.