Makefile: Move the completion-specific commands to completion/Makefile.local

For much better modularity.

Makefile

@@ -3,7 +3,7 @@
 all:
 
 # List all subdirectories here. Each contains its own Makefile.local
-subdirs = compat emacs lib
+subdirs = compat completion emacs lib
 
 # We make all targets depend on the Makefiles themselves.
 global_deps = Makefile Makefile.local \

Makefile.local

@@ -174,10 +174,6 @@ notmuch.1.gz: notmuch.1
 install: all notmuch.1.gz
 	mkdir -p $(DESTDIR)$(prefix)/share/man/man1
 	install -m0644 notmuch.1.gz $(DESTDIR)$(prefix)/share/man/man1/
-	mkdir -p $(DESTDIR)$(bash_completion_dir)
-	install -m0644 contrib/notmuch-completion.bash $(DESTDIR)$(bash_completion_dir)/notmuch
-	mkdir -p $(DESTDIR)$(zsh_completion_dir)
-	install -m0644 contrib/notmuch-completion.zsh $(DESTDIR)$(zsh_completion_dir)/notmuch
 	mkdir -p $(DESTDIR)$(prefix)/bin/
 	install notmuch-shared $(DESTDIR)$(prefix)/bin/notmuch
 ifeq ($(MAKECMDGOALS), install)

completion/Makefile

@@ -0,0 +1,7 @@
+# See Makfefile.local for the list of files to be compiled in this
+# directory.
+all:
+	$(MAKE) -C .. all
+
+.DEFAULT:
+	$(MAKE) -C .. $@

completion/Makefile.local

@@ -0,0 +1,18 @@
+# -*- makefile -*-
+
+dir := completion
+
+# The dir variable will be re-assigned to later, so we can't use it
+# directly in any shell commands. Instead we save its value in other,
+# private variables that we can use in the commands.
+bash_script := $(dir)/notmuch-completion.bash
+zsh_script := $(dir)/notmuch-completion.zsh
+
+install: install-$(dir)
+
+install-$(dir):
+	@echo $@
+	mkdir -p $(DESTDIR)$(bash_completion_dir)
+	install -m0644 $(bash_script) $(DESTDIR)$(bash_completion_dir)/notmuch
+	mkdir -p $(DESTDIR)$(zsh_completion_dir)
+	install -m0644 $(zsh_script) $(DESTDIR)$(zsh_completion_dir)/notmuch