Many systems expect a fsck.<filesystem> -a <device>
command to be accepted.

commit: 6cd836d7d95ae61edfca2406f48eeca47b8cfd81
(btrfs-progs: ignore -a option in mkfs)

added this 'support' to btrfsck so one could symlink fsck.btrfs
to btrfsck and get the desired result.

But then it got broken by:
commit 5956f752c66d5259bbb17a2dd47ee8c8cc0e5f4f
(Btrfs-progs: add btrfsck functionality to btrfs)

like this:
# fsck.btrfs -a /dev/loop0
Unknown option: -a
usage: btrfs [--help] [--version] <group> [<group>...] <command> [<args>]

Fix this breakage by doing the same name detection for fsck.btrfs as we do
for btrfsck as added in commit: d5d2046ae3b216af22a8a37c940f2412ba519b6e
(Btrfs-progs: add btrfsck name detection to btrfs)

and we get the expected result:

# fsck.btrfs -a /dev/loop0
Checking filesystem on /dev/loop0
UUID: afe796c5-9e06-43d2-a5f4-a2beca58e82a
checking extents
checking free space cache
cache and super generation don't match, space cache will be invalidated
checking fs roots
checking csums
checking root refs
found 28672 bytes used err is 0
total csum bytes: 0
total tree bytes: 28672
total fs tree bytes: 8192
total extent tree bytes: 4096
btree space waste bytes: 23766
file data blocks allocated: 0
 referenced 0
Btrfs v3.12

Signed-off-by: Thomas Backlund <tmb@mageia.org>

diff -Nurp btrfs-progs-v4.9.orig/btrfs.c btrfs-progs-v4.9/btrfs.c
--- btrfs-progs-v4.9.orig/btrfs.c
+++ btrfs-progs-v4.9/btrfs.c
@@ -217,7 +217,7 @@ int main(int argc, char **argv)
 	else
 		bname = argv[0];
 
-	if (!strcmp(bname, "btrfsck")) {
+	if (!strcmp(bname, "btrfsck") || !strcmp(bname, "fsck.btrfs")) {
 		argv[0] = "check";
 	} else {
 		argc--;