[Libguestfs] ANNOUNCE: "attach-method" is now "backend"

[Richard W.M. Jones]

Starting with libguestfs 1.22, "attach methods" will be known as
"backends" (one word, no space or hyphen).  There are new APIs
'guestfs_set_backend', 'guestfs_get_backend', and a new environment
variable 'LIBGUESTFS_BACKEND'.

Furthermore, the default backend, running qemu directly, is now called
"direct" instead of "appliance".  (Note that distros can change the
default by compiling with ./configure --with-default-backend=..., and
Fedora does change this to "libvirt").

FWIW there are three backends (same as before):

  - direct (a.k.a. appliance): Run qemu directly
  - libvirt: Manage the appliance with libvirt
  - unix: Connect to a Unix socket (for libguestfs live)

For backwards compatibility, the old APIs continue to be supported,
along with the LIBGUESTFS_ATTACH_METHOD environment variable, and the
synonym "appliance" instead of "direct".  Because these are part of
the C API they will be supported forever, but you can get a warning
about using them by compiling with -DGUESTFS_WARN_DEPRECATED=1.

See this large but mostly mechanical patch:

https://github.com/libguestfs/libguestfs/commit/68990840b64491b39ab8da5f1e46367ae5f01594

Also note this change will be included in RHEL 7.

Rich.

-- 
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