Add --exclude-other-filesystem support

[mafgh]

From duplicity:

--exclude-other-filesystems
Exclude files on file systems (identified by device number) other than the file system the root of the source directory is on.

Given

/dev/mapper/sys-root on /
proc on /proc
/dev/mapper/sys-home on /home

The following would backup / but not /home nor /proc

restic backup / --exclude-other-filesystem

[rfjakob]

This is pretty important when you want to back up the root filesystem and the one thing that keeps me from switching from Attic. I'll see if I can get this done.

[fd0]

Oh, that'd be excellent! If you have any questions or need guidance navigating the code base, feel free to drop by in #restic on irc.freenode.net :)

[fd0]

It was implemented and merged just now, the command-line option is --one-file-system.