Btrfs-progs: enhance btrfs subvol list only to show read-only snapshots

We want 'btrfs subvolume list' only to list readonly subvolumes, this patch set introduces a new option 'r' to implement it.

You can use the command like that:

btrfs subvolume list -r <mnt>

Changelog v3 -> v4:
- modify the check method which is used to check if btrfs_root_item contains otime and uuid or not.
- add filter set and comparer set which are used to manage the filters and comparers specified by the users.
- re-base the read-only subvolume list function.

Changelog v2 -> v3:
- re-implement list_subvols()
- re-implement this read-only subvolume list function based on the new list_subvols()

Changelog v1 -> v2:
- address the comments from Goffredo Baroncelli
i, change the changelog of the patches and make them more elaborate.
ii, move the function declarations to a new head file. iii, add the introduction of the new option 'r' into the man page

We can pull the patches from the URL

git://github.com/miaoxie/btrfs-progs.git master

This patchset is against the patches of Liu Bo, Anand Jain and mine which were sent by several days ago. And we also can pull those patches from the above URL.

Thanks
Miao
---
Miao Xie (5):
Btrfs-progs: fix compile warning of implicit declaration of "list_snapshots"
Btrfs-progs: fix wrong usage of btrfs subvolume list command
Btrfs-progs: fix wrong way to check if the root item contains otime and uuid
Btrfs-progs: restructure list_subvolumes
Btrfs-progs: enhance btrfs subvol list only to show read-only snapshots

Zhou Bo (2):
Btrfs-progs: move the function declarations to a new head file
Btrfs-progs: update the manpage entries for the btrfs subvolume list

 btrfs-list.c     | 1023 ++++++++++++++++++++++++++++++++----------------------
 btrfs-list.h     |   88 +++++
 cmds-inspect.c   |    6 +-
 cmds-subvolume.c |   78 ++++-
 ctree.h          |   17 +
 man/btrfs.8.in   |    5 +-
 send-utils.c     |    7 +-
 7 files changed, 786 insertions(+), 438 deletions(-)