Standardize on parens in Makefile, use CURDIR rather than $(shell pwd) (

#4369)

Makefile

@@ -1,11 +1,11 @@
 
 BUILD_DIR=build
-COVERAGE_DIR=${BUILD_DIR}/coverage
+COVERAGE_DIR=$(BUILD_DIR)/coverage
 BEATS=packetbeat filebeat winlogbeat metricbeat heartbeat
-PROJECTS=libbeat ${BEATS}
+PROJECTS=libbeat $(BEATS)
 PROJECTS_ENV=libbeat filebeat metricbeat
 SNAPSHOT?=yes
-PYTHON_ENV?=${BUILD_DIR}/python-env
+PYTHON_ENV?=$(BUILD_DIR)/python-env
 VIRTUALENV_PARAMS?=
 FIND=find . -type f -not -path "*/vendor/*" -not -path "*/build/*" -not -path "*/.git/*"
 GOLINT=golint
@@ -36,15 +36,15 @@ unit:
 
 .PHONY: coverage-report
 coverage-report:
-	mkdir -p ${COVERAGE_DIR}
+	mkdir -p $(COVERAGE_DIR)
 	# Writes atomic mode on top of file
-	echo 'mode: atomic' > ./${COVERAGE_DIR}/full.cov
+	echo 'mode: atomic' > ./$(COVERAGE_DIR)/full.cov
 	# Collects all coverage files and skips top line with mode
-	-tail -q -n +2 ./filebeat/${COVERAGE_DIR}/*.cov >> ./${COVERAGE_DIR}/full.cov
-	-tail -q -n +2 ./packetbeat/${COVERAGE_DIR}/*.cov >> ./${COVERAGE_DIR}/full.cov
-	-tail -q -n +2 ./winlogbeat/${COVERAGE_DIR}/*.cov >> ./${COVERAGE_DIR}/full.cov
-	-tail -q -n +2 ./libbeat/${COVERAGE_DIR}/*.cov >> ./${COVERAGE_DIR}/full.cov
-	go tool cover -html=./${COVERAGE_DIR}/full.cov -o ${COVERAGE_DIR}/full.html
+	-tail -q -n +2 ./filebeat/$(COVERAGE_DIR)/*.cov >> ./$(COVERAGE_DIR)/full.cov
+	-tail -q -n +2 ./packetbeat/$(COVERAGE_DIR)/*.cov >> ./$(COVERAGE_DIR)/full.cov
+	-tail -q -n +2 ./winlogbeat/$(COVERAGE_DIR)/*.cov >> ./$(COVERAGE_DIR)/full.cov
+	-tail -q -n +2 ./libbeat/$(COVERAGE_DIR)/*.cov >> ./$(COVERAGE_DIR)/full.cov
+	go tool cover -html=./$(COVERAGE_DIR)/full.cov -o $(COVERAGE_DIR)/full.html
 
 .PHONY: update
 update: notice
@@ -66,7 +66,7 @@ clean-vendor:
 check: python-env
 	$(foreach var,$(PROJECTS),$(MAKE) -C $(var) check || exit 1;)
 	# Checks also python files which are not part of the beats
-	${FIND} -name *.py -exec autopep8 -d --max-line-length 120  {} \; | (! grep . -q) || (echo "Code differs from autopep8's style" && false)
+	$(FIND) -name *.py -exec autopep8 -d --max-line-length 120  {} \; | (! grep . -q) || (echo "Code differs from autopep8's style" && false)
 	# Validate that all updates were committed
 	$(MAKE) update
 	git diff | cat
@@ -83,7 +83,7 @@ misspell:
 fmt: python-env
 	$(foreach var,$(PROJECTS),$(MAKE) -C $(var) fmt || exit 1;)
 	# Cleans also python files which are not part of the beats
-	. ${PYTHON_ENV}/bin/activate && find . -type f -name *.py -not -path "*/vendor/*" -not -path "*/build/*" -not -path "*/.git/*" -exec autopep8 --in-place --max-line-length 120  {} \;
+	. $(PYTHON_ENV)/bin/activate && find . -type f -name *.py -not -path "*/vendor/*" -not -path "*/build/*" -not -path "*/.git/*" -exec autopep8 --in-place --max-line-length 120  {} \;
 
 .PHONY: lint
 lint:
@@ -99,7 +99,7 @@ beats-dashboards:
 # Builds the documents for each beat
 .PHONY: docs
 docs:
-	sh libbeat/scripts/build_docs.sh ${PROJECTS}
+	sh libbeat/scripts/build_docs.sh $(PROJECTS)
 
 .PHONY: package
 package: update beats-dashboards
@@ -108,15 +108,15 @@ package: update beats-dashboards
 	# build the dashboards package
 	echo "Start building the dashboards package"
 	mkdir -p build/upload/
-	BUILD_DIR=${shell pwd}/build SNAPSHOT=$(SNAPSHOT) $(MAKE) -C dev-tools/packer package-dashboards ${shell pwd}/build/upload/build_id.txt
+	BUILD_DIR=$(CURDIR)/build SNAPSHOT=$(SNAPSHOT) $(MAKE) -C dev-tools/packer package-dashboards $(CURDIR)/build/upload/build_id.txt
 	mv build/upload build/dashboards-upload
 
 	# Copy build files over to top build directory
 	mkdir -p build/upload/
 	$(foreach var,$(BEATS),cp -r $(var)/build/upload/ build/upload/$(var)  || exit 1;)
 	cp -r build/dashboards-upload build/upload/dashboards
 	# Run tests on the generated packages.
-	go test ./dev-tools/package_test.go -files "${shell pwd}/build/upload/*/*"
+	go test ./dev-tools/package_test.go -files "$(CURDIR)/build/upload/*/*"
 
 # Upload nightly builds to S3
 .PHONY: upload-nightlies-s3
@@ -142,5 +142,5 @@ notice:
 # Sets up the virtual python environment
 .PHONY: python-env
 python-env:
-	@test -d ${PYTHON_ENV} || virtualenv ${VIRTUALENV_PARAMS} ${PYTHON_ENV}
-	@. ${PYTHON_ENV}/bin/activate && pip install -q --upgrade pip autopep8
+	@test -d $(PYTHON_ENV) || virtualenv $(VIRTUALENV_PARAMS) $(PYTHON_ENV)
+	@. $(PYTHON_ENV)/bin/activate && pip install -q --upgrade pip autopep8