Add ability to pass arbitrary extra arguments to git log

[t-gehring]

Describe the feature that you'd like A number of current feature requests essentially boil down to "expose this existing git log argument". While having nice UI tools for these various features is wonderful, being able to just add the commandline arguments would be a great stop-gap for some of the features which require a lot more development work.

Additional context Some existing issues which would have workarounds if this was added:

• #147 (and thus also #70 and #171 and #375)
  • filter by file/tree, author, date range, grepping the commit message, inverting the grep search
• #257 (--remotes[=<pattern>])
• #360 (which has been partially done via the settings, but can't be done on the fly)
• #387 (Somewhat provided by --simplify-by-decoration)
• #465 (--tags[=<pattern>])

Plus various other things that haven't yet been requested as features:

• --bisect for only showing the portion of the graph relevant to the current git bisect
• excluding commits reachable from certain points
• various options for performing comparisons between points
• change the sort order for commits
• --single-worktree for only showing commits in the current worktree
• various simplification options, like omitting merges, simplifying merges
• any features in a future version of git log which are not currently available

There are also several features which have been added now as proper UI options, but which would have had workarounds available earlier via this (--reflog, --first-parent, show stashes, potentially others). It's great that these have been implemented into the UI, but I recognise you have limited time to work on this extension, so it would be nice to have a way to use these features without needing to take up your development time.