Reversed the order of reference prefixes tried when matching a config
section from least significant first to most significant first.

Shell globing disabled around the retrieval of section names (which
are ref patterns) to prevent matching file paths.

This reverts commit 1600e768.

Config section names (which are ref patterns) quoted to prevent
matching file paths.

auto-build commands that use shell operations like '&&' need to
actually invoke the shell. The autoconf profile command now
invokes 'bash -c "... && ..."'

To avoid unexpected permissions on build files the build directories
must not have a sticky bit set. The bit is unset on directory creation.

To support relative links `readlink -f ...` was used on the build
command. The problem with this is if arguments are included in the
build command it breaks. The command line is now broken up and
`readline -e ...` run on the first part. (-e ensures that the target
exists.)

All the build subshells attempted to lock with the parent shell's PID,
so could not exclude each other from build environments.

Log files are now in /tmp/build/$ref/

Commands can now be specified relative to the build repo and an
environment variable (AUTO_BUILD_BASE) was added for scripts to
find objects relative to the repo.

_find_config_section can handle missing leading parts like refs/,
refs/heads/, tags/, etc.

This ensures that in empty build directories there is a working tree
to be cleaned when the commands are called.

Fixed the order of section matching so that more specific matches are
ordered before less specific matches. Also hugely simplified and
streamlined the search code.

Added the auto-build hook which is a bit of a beast. It lacks
documentation at the moment so here is a git config reminder with
defaults:

[auto-build]
	location = /tmp/build/
	max-build = 4
[auto-build "refs/...[*]"]
	destination = /tmp
	backup = yes
	profile = <auto detected>
	command = <from profile>
	pattern = <from profile>

enable & disable originally tried only to set or unset the executable
bit on a file, which is not a viable method with links to shared hook
scripts. They now change the target of links, prepending 'disabled:' to
disabled links.

The init command reads a comma-separated list of hook scripts to install
from git-hooks.$hook, unless the --ignore-defaults argument is given.

init command has a new --keep argument that packs any old hook.d
directories that do not appear to be from git-hooks into tar files.
--force now simply removes old versions so --keep is effectively doing
what --force used to do.