Allow more complex parameters

[thomasjachmann]

This will allow to combine the bang command with additional parameters and also include placeholders % and + in your command parameters that will be expanded into the current file path and the cursor's line number.

This way, you can create all kinds of calls to tig like:

• Tig! blame + to get a blame view of the current file with the current line highlighted
• Tig! main --first-parent get a list of all direct commits to the current file on the current branch

The file name placeholder expansion is a bit redundant with the bang command version but I just included it so maybe some specific uses that require a more complex command setup might work.