Portable makefile with creating directories

Test bash-completion before installing completions and removing them

makefile

@@ -1,11 +1,15 @@
 install:
 	@echo "Installing git ommix !"
-	install -Dm755 git-ommix /bin/git-ommix
-	install -Dm644 functions /usr/share/git-ommix/functions
-	install -Dm644 example.conf /etc/gitommix.conf
-	install -Dm644 gitommix-completions /usr/share/bash-completion/completions/git-ommix
+	install -m755 git-ommix /usr/bin/git-ommix
+	install -m644 example.conf /etc/gitommix.conf
+
+	mkdir -p /usr/share/git-ommix
+	install -m644 functions /usr/share/git-ommix/functions
+
+	[ -d /usr/share/bash-completion/completions ] && install -m644 gitommix-completions /usr/share/bash-completion/completions/git-ommix
 
 uninstall:
 	@echo "Uninstalling…"
-	rm -rf /bin/git-ommix
+	rm -rf /usr/bin/git-ommix
 	rm -rf /usr/share/git-ommix
+	[ -d /usr/share/bash-completion/completions ] && rm -rf /usr/share/bash-completion/completions/git-ommix