Add new index.txt script

This commit goes with the previous one—the commit is in two pieces so
that git can tell that this new index.txt isn't just a modification the
old one, but rather a totally new file.

This script supports being run as the installation entrypoint when
downloaded as part of the one-line web install (though it'll tell you
that you should install it the "more proper way"), but doesn't run from
inside the source tree.

The new script actually solves a race condition that could happen if
someone were installing literally while the repository was being
upgraded.  You might find new versions of say a2server-5-netboot
being downloaded and run which depend on an a2server-3-sharing that
didn't get upgraded.  The new index.txt will always download all of the
scripts together in a cohesive revision at once.

The only possible code version mismatch now is between index.txt and
everything else, and the only updates planned for index.txt going
forward are textual changes telling you how to download the tarball and
run the installer yourself.

setup/index.txt

@@ -0,0 +1,100 @@
+#! /bin/bash
+# vim: set tabstop=4 shiftwidth=4 noexpandtab filetype=sh:
+
+# setup/index.txt - upgrade path from Ivan's a2server tree
+#
+# Ivan's a2server installed with a single copy-paste of a command line that
+# downloaded a script and ran it sight-unseen.  People are going to continue
+# to run that command (they shouldn't, but they will), and we can support
+# them doing it for now.
+
+a2sBranch="master"
+a2sScriptURL="https://raw.githubusercontent.com/RasppleII/a2server/${a2sBranch}"
+a2sTarball="https://github.com/RasppleII/a2server/archive/${a2sBranch}.tar.gz"
+
+origDir="$PWD"
+
+# Set a2sDevel to the location of the source tree if we're running in one
+a2sDevel="$( dirname "${BASH_SOURCE[0]}" )/.."
+if [[ -f "$a2sDevel/.a2server_source" ]]; then
+	pushd $a2sDevel >/dev/null
+	a2sDevel="$PWD"
+	popd >/dev/null
+
+	cat <<-EOT
+	This script exists solely for backward-compatibility with IvanX's a2server
+	website and aliases installed by older versions.  You appear to have an
+	a2server source directory here:
+	 	$a2sDevel
+
+	Please run ./install.sh in that directory.  Thanks!
+
+	EOT
+	exit 1
+fi
+a2sDevel=
+
+# Find the version in the install script
+newVersion=$(wget -qO- "${a2sScriptURL}/install.sh" | grep '^a2serverVersion' | cut -d '"' -f 2)
+
+
+# It almost never is, but this script could be run with command line arguments,
+# of which -y we can use, so we should check for it.  We'll pass them all to
+# the install script later
+autoAnswerYes=
+for arg in $@; do
+	if [[ $arg == "-y" ]]; then
+		autoAnswerYes=1
+		break
+	fi
+done
+
+
+
+cat <<EOT
+
+Hello, you've reached the single wget command version of the a2server install
+script.  This script is being phased out for a number of reasons.  The most
+important is that it is not repeatable.  This script will download things
+behind the scenes, run them without much verification, and then delete what it
+ran, no matter if the installation finished successfully or not.  The next
+time you run the same command, you may get a different (hopefully better)
+version.
+
+Right now, a2server ${newVersion} is available.
+
+If you are seeing this text, iKarith (Joseph Carter) hasn't bothered to write
+publicly-facing end-user documentation for downloading and installing a2server
+a more preferred way.  He's filed an issue about this, please do follow the
+instructions there:
+	https://github.com/RasppleII/a2server/issues/60
+
+For now, this script does what the old installer used to.
+
+EOT
+
+if [[ ! $autoAnswerYes ]]; then
+	printf "Do you want to install a2server with this script? "
+	read
+	if [[ ${REPLY:0:1} != "y" && ${REPLY:0:1} != "Y" ]]; then
+		printf "\nOkay, not installing anything now!\n\n"
+		exit 1
+	fi
+fi
+
+a2sInstall=$(mktemp -d /tmp/a2server.XXXXXXXXXXXX)
+cd "$a2sInstall"
+
+# We rename the tarball we download for consistency
+printf "\na2server: Downloading installer to ${a2sInstall}.\n"
+wget -O "a2server-${a2sBranch}.tar.gz" "$a2sTarball"
+tar zxf "a2server-${a2sBranch}.tar.gz"
+
+# Now we actually run the installer
+printf "\na2server: Running the installer now.\n"
+"a2server-${a2sBranch}/install.sh" "$@"
+
+# Clean up and delete the installer we downloaded
+printf "\na2server: Finished with installer, now deleting ${a2sInstall}.\n"
+cd "$origDir"
+rm -rf "$a2sInstall"