move completions into their own directory

And add infrastructure for installing bash-completions

Makefile

@@ -39,7 +39,10 @@ check: all
 install: all
 	install -dm755 $(DESTDIR)$(PREFIX)/bin
 	install -m755 $(BINPROGS) $(DESTDIR)$(PREFIX)/bin
-	install -Dm644 zsh-completion $(DESTDIR)$(PREFIX)/share/zsh/site-functions/_archinstallscripts
+	install -Dm644 completion/_archinstallscripts.zsh $(DESTDIR)$(PREFIX)/share/zsh/site-functions/_archinstallscripts
+	cd completion; for comp in *.bash; do \
+		install -Dm644 $$comp $(DESTDIR)$(PREFIX)/share/bash-completion/completions/$${comp%%.*}; \
+	done;
 	for manfile in $(MANS); do \
 		install -Dm644 $$manfile -t $(DESTDIR)$(PREFIX)/share/man/man$${manfile##*.}; \
 	done;