Add recursive dependency fetching to the Makefile

Also small other changes like how we build the PLT.

Makefile

@@ -4,6 +4,9 @@ PROJECT = cowboy
 RANCH_VSN = 0.6.0
 ERLC_OPTS = -Werror +debug_info +warn_export_all # +bin_opt_info +warn_missing_spec
 
+DEPS_DIR ?= $(CURDIR)/deps
+export DEPS_DIR
+
 .PHONY: all clean-all app clean docs clean-docs tests autobahn build-plt dialyze
 
 # Application.
@@ -12,25 +15,26 @@ all: app
 
 clean-all: clean clean-docs
 	rm -f .$(PROJECT).plt
-	rm -rf deps logs
+	rm -rf $(DEPS_DIR) logs
 
 deps/ranch:
-	@mkdir -p deps/
-	git clone -n -- https://github.com/extend/ranch.git deps/ranch
-	cd deps/ranch ; git checkout -q $(RANCH_VSN)
+	@mkdir -p $(DEPS_DIR)
+	git clone -n -- https://github.com/extend/ranch.git $(DEPS_DIR)/ranch
+	cd $(DEPS_DIR)/ranch ; git checkout -q $(RANCH_VSN)
 
 MODULES = $(shell ls src/*.erl | sed 's/src\///;s/\.erl/,/' | sed '$$s/.$$//')
 
 app: deps/ranch
-	@cd deps/ranch ; make
+	@$(MAKE) -C $(DEPS_DIR)/ranch
 	@mkdir -p ebin/
-	@cat src/cowboy.app.src \
+	@cat src/$(PROJECT).app.src \
 		| sed 's/{modules, \[\]}/{modules, \[$(MODULES)\]}/' \
-		> ebin/cowboy.app
-	erlc -v $(ERLC_OPTS) -o ebin/ -pa ebin/ src/cowboy_middleware.erl src/*.erl
+		> ebin/$(PROJECT).app
+	erlc -v $(ERLC_OPTS) -o ebin/ -pa ebin/ \
+		src/$(PROJECT)_middleware.erl src/*.erl
 
 clean:
-	-@cd deps/ranch && make clean
+	-@$(MAKE) -C $(DEPS_DIR)/ranch clean
 	rm -rf ebin/
 	rm -f test/*.beam
 	rm -f erl_crash.dump
@@ -38,7 +42,7 @@ clean:
 # Documentation.
 
 docs: clean-docs
-	erl -noshell -eval 'edoc:application(cowboy, ".", []), init:stop().'
+	erl -noshell -eval 'edoc:application($(PROJECT), ".", []), init:stop().'
 
 clean-docs:
 	rm -f doc/*.css
@@ -49,7 +53,7 @@ clean-docs:
 # Tests.
 
 CT_RUN = ct_run \
-	-pa ebin deps/*/ebin \
+	-pa ebin $(DEPS_DIR)/*/ebin \
 	-dir test \
 	-logdir logs \
 	-cover test/cover.spec
@@ -67,7 +71,7 @@ autobahn: clean app
 
 build-plt: app
 	@dialyzer --build_plt --output_plt .$(PROJECT).plt \
-		--apps erts kernel stdlib sasl inets crypto public_key ssl deps/ranch
+		--apps erts kernel stdlib crypto public_key ssl $(DEPS_DIR)/ranch
 
 dialyze:
 	@dialyzer --src src --plt .$(PROJECT).plt --no_native \