ci(Makefile): added help and descriptions to targets (#3964)

Author: tr1sm0s1n

Makefile

@@ -8,6 +8,7 @@ TESTFOLDER := $(shell $(GO) list ./... | grep -E 'gin$$|binding$$|render$$' | gr
 TESTTAGS ?= ""
 
 .PHONY: test
+# Run tests to verify code functionality.
 test:
 	echo "mode: count" > coverage.out
 	for d in $(TESTFOLDER); do \
@@ -30,10 +31,12 @@ test:
 	done
 
 .PHONY: fmt
+# Ensure consistent code formatting.
 fmt:
 	$(GOFMT) -w $(GOFILES)
 
 .PHONY: fmt-check
+# format (check only).
 fmt-check:
 	@diff=$$($(GOFMT) -d $(GOFILES)); \
 	if [ -n "$$diff" ]; then \
@@ -43,31 +46,36 @@ fmt-check:
 	fi;
 
 .PHONY: vet
+# Examine packages and report suspicious constructs if any.
 vet:
 	$(GO) vet $(VETPACKAGES)
 
 .PHONY: lint
+# Inspect source code for stylistic errors or potential bugs.
 lint:
 	@hash golint > /dev/null 2>&1; if [ $$? -ne 0 ]; then \
 		$(GO) get -u golang.org/x/lint/golint; \
 	fi
 	for PKG in $(PACKAGES); do golint -set_exit_status $$PKG || exit 1; done;
 
-.PHONY: misspell-check
-misspell-check:
+.PHONY: misspell
+# Correct commonly misspelled English words in source code.
+misspell:
 	@hash misspell > /dev/null 2>&1; if [ $$? -ne 0 ]; then \
 		$(GO) get -u github.com/client9/misspell/cmd/misspell; \
 	fi
-	misspell -error $(GOFILES)
+	misspell -w $(GOFILES)
 
-.PHONY: misspell
-misspell:
+.PHONY: misspell-check
+# misspell (check only).
+misspell-check:
 	@hash misspell > /dev/null 2>&1; if [ $$? -ne 0 ]; then \
 		$(GO) get -u github.com/client9/misspell/cmd/misspell; \
 	fi
-	misspell -w $(GOFILES)
+	misspell -error $(GOFILES)
 
 .PHONY: tools
+# Install tools (golint and misspell).
 tools:
 	@if [ $(GO_VERSION) -gt 15 ]; then \
 		$(GO) install golang.org/x/lint/golint@latest; \
@@ -76,3 +84,23 @@ tools:
 		$(GO) install golang.org/x/lint/golint; \
 		$(GO) install github.com/client9/misspell/cmd/misspell; \
 	fi
+
+.PHONY: help
+# Help.
+help:
+	@echo ''
+	@echo 'Usage:'
+	@echo ' make [target]'
+	@echo ''
+	@echo 'Targets:'
+	@awk '/^[a-zA-Z\-\0-9]+:/ { \
+	helpMessage = match(lastLine, /^# (.*)/); \
+		if (helpMessage) { \
+			helpCommand = substr($$1, 0, index($$1, ":")-1); \
+			helpMessage = substr(lastLine, RSTART + 2, RLENGTH); \
+			printf " - \033[36m%-20s\033[0m %s\n", helpCommand, helpMessage; \
+		} \
+	} \
+	{ lastLine = $$0 }' $(MAKEFILE_LIST)
+
+.DEFAULT_GOAL := help