Update Makefile to assume a single package

Makefile

@@ -1,45 +1,60 @@
 export GO15VENDOREXPERIMENT=1
 
 BENCH_FLAGS ?= -cpuprofile=cpu.pprof -memprofile=mem.pprof -benchmem
-PACKAGES ?= $(shell glide novendor)
+PKGS ?= $(shell glide novendor)
+# Many Go tools take file globs or directories as arguments instead of packages.
+PKG_DIRS ?= *.go
+
+# The linting tools evolve with each Go version, so run them only on the latest
+# stable release.
+GO_VERSION := $(shell go version | cut -d " " -f 3)
+GO_MINOR_VERSION := $(word 2,$(subst ., ,$(GO_VERSION)))
+LINTABLE_MINOR_VERSIONS := 6
+ifneq ($(filter $(LINTABLE_MINOR_VERSIONS),$(GO_MINOR_VERSION)),)
+SHOULD_LINT := true
+endif
+
 
 .PHONY: all
 all: lint test
 
 .PHONY: dependencies
 dependencies:
+	@echo "Installing Glide and locked dependencies..."
 	glide --version || go get -u -f github.com/Masterminds/glide
 	glide install
-	go install ./vendor/github.com/golang/lint/golint
+	@echo "Installing test dependencies..."
 	go install ./vendor/github.com/axw/gocov/gocov
 	go install ./vendor/github.com/mattn/goveralls
+ifdef SHOULD_LINT
+	@echo "Installing golint..."
+	go install ./vendor/github.com/golang/lint/golint
+else
+	@echo "Not installing golint, since we don't expect to lint on" $(GO_VERSION)
+endif
 
 .PHONY: lint
 lint:
 	@rm -rf lint.log
 	@echo "Checking formatting..."
-	@gofmt -d -s *.go benchmarks encoder 2>&1 | tee lint.log
+	@gofmt -d -s $(PKG_DIRS) 2>&1 | tee lint.log
 	@echo "Checking vet..."
-	@go tool vet *.go 2>&1 | tee -a lint.log
-	@go tool vet benchmarks 2>&1 | tee -a lint.log
-	@go tool vet encoder 2>&1 | tee -a lint.log
+	@$(foreach dir,$(PKG_DIRS),go tool vet $(dir) 2>&1 | tee -a lint.log;)
 	@echo "Checking lint..."
-	@golint . 2>&1 | tee -a lint.log
-	@golint benchmarks 2>&1 | tee -a lint.log
-	@golint encoder 2>&1 | tee -a lint.log
+	@$(foreach dir,$(PKG_DIRS),golint $(dir) 2>&1 | tee -a lint.log;)
 	@echo "Checking for unresolved FIXMEs..."
 	@git grep -i fixme | grep -v -e vendor -e Makefile | tee -a lint.log
 	@[ ! -s lint.log ]
 
 .PHONY: test
 test:
-	go test -race $(PACKAGES)
+	go test -race $(PKGS)
 
 .PHONY: coveralls
 coveralls:
-	goveralls -service=travis-ci $(PACKAGES)
+	goveralls -service=travis-ci $(PKGS)
 
 .PHONY: bench
 BENCH ?= .
 bench:
-	go test -bench=$(BENCH) $(BENCH_FLAGS) ./benchmarks
+	go test -bench=$(BENCH) $(BENCH_FLAGS) .