Note to self: never try to move submodules again

To migrate your existing submodules (more or less):

	set -x
	set -e

	mkdir .git/modules/pkg
	for old in */*/src ; do
	        new="pkg/${old#*/}"
	        if ! [ -f "$old/.git" ] || [ "${old%%/*}" = pkg ] ; then
			continue
		fi
		git -C ".git/modules/$old" config core.worktree "../../../../../$new"
		rmdir "$new"
		mv "$old" "$new"
	        sed -e "s,$old,$new," "$new/.git" > "$new/.git.tmp"
	        mv "$new/.git.tmp" "$new/.git"
		mkdir ".git/modules/${new%/src}"
	        mv ".git/modules/$old" ".git/modules/$new"

		rm "${old%/src}"/*.ninja
		mv "${old%/src}"/*.tar.{gz,xz,bz2} "${new%/src}/"
		rmdir "${old%/src}" || true
	done
	sed -e 's,^\[submodule "[^/]*/,[submodule "pkg/,' .git/config > .git/config.tmp
	mv .git/config.tmp .git/config

There is little chance of collision between phony target names and actual
sources checked in $dir. Additionally, it was a bit magical when processing
phony sources because paths starting with $ or phony/ were left alone, while
others were prepended with $outdir/.

Also, where appropriate, use phony targets for dependencies instead of
specifying all of them for every compile action. This makes the resulting ninja
files easier to read, and might be more efficient too.