Avoid complaining that a file with "is beyond a symbolic link" when the
filepath is absolute and the symlink in question is not actually inside the
git repository.
This assumes that inodes remain stable while the command is running.
I think they always will, the filesystems where they are unstable change
them across mounts. (If inodes were not stable, it would just complain about
symlinks in the path that are not inside the working tree.)
(On windows, I don't want to assume anything about inodes, they could be
random numbers for all I know. But if they were, this would still be ok, as
long as windows doesn't have symlinks that are detected by isSymbolicLink.
Which seems a fair bet.)
Part of workTreeItems is trying detect a case
where git porcelain refuses to process a file, and where
git ls-files silently outputs nothing. But, it's hard to perfectly
replicate git's behavior, and besides, git's behavior could change.
So it could be that we warn, but then git ls-files does not skip over
it, and so git-annex also processes it after warning about it.
So, if we think we have a problem with a parameter, display the warning,
and skip processing it at all.
Implementing this was complicated by needing to handle the case where
all command-line parameters get filtered out this way. Which is
different than the case where there are none, because we don't want to
operate on all files in this new case..
