最近正在狂暴写毕设，大量阅读代码，在 Tailscale 的仓库里看到颇为有趣的一个 Makefile Target：

help: ## Show this help
	@echo ""
	@echo "Specify a command. The choices are:"
	@echo ""
	@grep -hE '^[0-9a-zA-Z_-]+:.*?## .*$$' ${MAKEFILE_LIST} | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "  \033[0;36m%-20s\033[m %s\n", $$1, $$2}'
	@echo ""
.PHONY: help

.DEFAULT_GOAL := help

该 Target 的作用是输出本 Makefile 文件里所有带有##的行，然后以冒号和##为分隔符，把 target 和##后的内容输出出来。

效果就像是这样的：

❯ make

Specify a command. The choices are:

  build386             Build tailscale CLI for linux/386
  buildlinuxarm        Build tailscale CLI for linux/arm
  buildlinuxloong64    Build tailscale CLI for linux/loong64
  buildmultiarchimage  Build (and optionally push) multiarch docker image
  buildwasm            Build tailscale CLI for js/wasm
  buildwindows         Build tailscale CLI for windows/amd64
  check                Perform basic checks and compilation tests
  depaware             Run depaware checks
  generate             Generate code
  help                 Show this help
  kube-generate-all    Refresh generated files for Tailscale Kubernetes Operator
  kube-generate-deepcopy Refresh generated deepcopy functionality for Tailscale kube API types
  lint                 Run golangci-lint
  publishdevimage      Build and publish tailscale image to location specified by ${REPO}
  publishdevnameserver Build and publish k8s-nameserver image to location specified by ${REPO}
  publishdevoperator   Build and publish k8s-operator image to location specified by ${REPO}
  publishdevproxy      Build and publish k8s-proxy image to location specified by ${REPO}
  publishdevtsidp      Build and publish tsidp image to location specified by ${REPO}
  pushspk              Push and install synology package on ${SYNO_HOST} host
  spkall               Build synology packages for all architectures and DSM versions
  spk                  Build synology package for ${SYNO_ARCH} architecture and ${SYNO_DSM} DSM version
  sshintegrationtest   Run the SSH integration tests in various Docker containers
  staticcheck          Run staticcheck.io checks
  tidy                 Run go mod tidy and update nix flake hashes
  updatedeps           Update depaware deps
  vet                  Run go vet

感觉效果非常好。

.DEFAULT_GOAL 这个变量也有意思，指定了 Makefile 默认的 Target。所以上面执行make的时候都没加help这个 Target。

挺好用的。