[Libguestfs] PATCH: Allow specifying the filesystem driver for guestmount

[Dave Vasilevsky]

Currently guestfish has mount-vfs, and the libguestfs API has
guestfs_mount_vfs(), but guestmount doesn't allow the user to specify
a filesystem. This patch extends the --mount argument, so you can
force an ext2 partition to mount as ext4:

  guestmount -a mydisk.img -m /dev/vda:/:defaults:ext4 mountpoint

You could also use it to choose between ntfs and ntfs-3g, or between
hfsplus and the commercial ufsd. Finally, it could be useful if blkid
misidentifies the filesystem.

GitHub compare doodad: https://github.com/vasi/libguestfs/compare/fuse-fstype
Patch: https://github.com/vasi/libguestfs/compare/fuse-fstype.patch

Thanks for making such a useful utility!
-V