ENH: Allow to override original buffer name passed to the external VCS command via <VCSCOMMANDFILE:.*>

This can be useful e.g. in diff to show a diff across the repository (by passing nothing / the repository root dir), not just for the original buffer.
Merge branch 'repeat-annotate-with-predecessor'
Merge branch 'additional-hooks'
Merge branch 'enh-annotate'

Conflicts:
	plugin/vcscommand.vim
Merge branch 'support-svn-blame-g-sigil'
Merge branch 'enh-VCSCommandCommandHook'
Merge branch 'enh-VCSCOMMANDFILE'

Conflicts:
	plugin/vcscommand.vim