Copyright-holder and year information is extracted from git log.
git history begins in 2005. So (C) from 1998..2005 is lost. Also some
(C) assignment of commits where the committer didn't use --author.
This fixes an issue on MacOS/X to only show non-root volumes in
the file-open dialog. They're just as valid for save-as, export, video
files etc.
In case of a 2nd internal disk, it is also a valid choice as default
folder for new sessions.
When a non-existent file-path is given, GTK falls back to show the
containing folder and automatically goes up to parent folders until
the root.
This removes the explicit file/folder check and delegates the
behavior to GTK, allowing to set a folder for a non-existent file.