Add a log menu option to filter the commit graph by refs

[alexeRadu]

Sometimes you want the graph limited to a handful of branches or tags rather than just the checked-out branch or the entire --all graph. Add a "Filter graph by refs" entry to the log menu that prompts for space-separated ref names and passes them to git log as extra starting points alongside the current ref.

PR Description

Please check if the PR fulfills these requirements

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