The added PKGBUILD.proto file is so that shellcheck can know know what
to expect that a PKGBUILD sets.

The default m4 quote characters: `QUOTE' are troublesome, because ` is
fairly likely to pop up in a shell script (if not for a subshell, because
it is a useful character in comments and user-facing messages).

So, this changes it to [[[QUOTE]]], as it is unlikely to see three braces
together like that, let alone in unbalanced sets.

The absence of it was allowing an (m4-produced) syntax error in
in a change I had made to be masked.

This makes it a lot easier to swap out the host that actually serves the repos in the future.

It's an xmas miracle!

For example...

$ make
GEN checkpkg
GEN commitpkg
GEN archco
archco: line 179: unexpected EOF while looking for matching `"'
archco: line 181: syntax error: unexpected end of file
make: *** [archco] Error 2

Signed-off-by: Dave Reisner <dreisner@archlinux.org>
Signed-off-by: Pierre Schmitz <pierre@archlinux.de>

Separates the two features of mkarchroot. Provides users of the new
arch-nspawn with the full feature set of systemd-nspawn.

For example, this can be used to bind custom directories into the chroot.