[Libguestfs] [PATCH nbdkit v3 0/4] Add linuxdisk plugin.

For v3 I reimplemented this using mke2fs -d. This obviously makes the implementation a whole lot simpler, but cannot support multiple directory merging. Patches 1-3 are the same as before. I've also reproduced the notes from v2 below. v2: - Fix inconsistent tab/space. - All 3 plugins now contain a block of text pointing to the other 2 plugins. - TMDIR -> TMPDIR - Unlink the temporary file and other cleanups along error paths. - fclose -> pclose, and check the return value for errors. I considered, but didn't yet fix, the latent bug in shell_quote. Instead I added a comment. Note there's a case where we probably (arguably) should be using shell_quote on an argv[0] here: https://github.com/libguestfs/nbdkit/blob/72e0afe2e280d895f68941677fafa55... 'du -c -k -s' works on FreeBSD which doesn't have GNU coreutils. (However I agree it's not very natural to use this plugin with FreeBSD at all.) Rich.