Bugfix: Fix unquoting when line has multiple file names

[eKoopmans]

• On rename/copy events, the Git status line reports two files: file1 -> file2
• If both filenames were quoted ("file1" -> "file2"), brackets-git was stripping the external quotes, leaving a malformed line (file1" -> "file2) and a corrupt filename "file2
• This PR corrects the issue by parsing the -> separator first, while leaving all other behaviour intact

[eKoopmans]

There is one other extreme case worth considering (which would require another slight rewrite to the logic):

• If a filename contains "->" (only possible on Mac/*nix), the logic will fail and split the filename at that point.

This issue is present in both the original code and after my current commit.

[Amro1984]