compat: make topics compatible across change to cmdutil.commitstatus()
`cmdutil.commitstatus()` was changed in https://phab.mercurial-scm.org/D9257 so it has a new `tip` argument. This patch adds compatibility with that. It was harder than I expected because the callers all pass the arguments as positional, so we can't look for `opts` or `tip` in the `kwargs`. I instead extracted much of the override to a helper. I think the result is okay.
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