Expand arguments support for SCMTool.popen().
Review Request #11804 — Created Sept. 1, 2021 and submitted
SCMTool.popen()previously had a hard-coded list of arguments that
were supported, which wasn't particularly helpful for many use cases.
Now, it takes
**kwargsand passes them to
also allows for overriding the pipes, if needed by the caller.
Made use of this in an upcoming SCM implementation.