Golang automatic Makefile.

Makefile

################################################################################
# Golang automatic Makefile                                                    #
################################################################################

##
#
# @author Jay Taylor <jay@gigawatt.io>
#
# @date 2015-05-20
#
# @description Automatically builds go projects, including ones with nested
# packages.
#
##

MAKEFLAGS += --warn-undefined-variables
SHELL := bash
#.SHELLFLAGS := -o errexit -o pipefail -o nounset -o xtrace -c
.SHELLFLAGS := -o errexit -o pipefail -o nounset -c

RM := rm -rf

# Automatically discover all buildable targets.
BUILDABLE_PACKAGES := $(shell \
	test -r .Makefile.packages.cache && cat .Makefile.packages.cache \
	|| \
	find . \
		-not \( -path ./Godeps -prune \) \
		-type f \
		-name "*.go" \
		-exec bash -c 'test -n "`tr "\n" " " < "{}" | grep "^package main .* func main() { .* }"`" && echo {}' \; \
	| xargs -n1 -IX bash -c '( cd "`dirname "X"`" && go list && cd - 1>/dev/null ) | sed "s|^\([^\/]*\/\)\{0,1\}\(.*\)|`dirname "X"`\/\2:`dirname "X"`|"' \
	| tee .Makefile.cache \
)

BUILD_DATE := $(shell date +%Y-%m-%dT%H:%M:%S%z)
BUILD_HASH := $(shell git log -1 | head -n 1 | cut -d ' ' -f 2)


all: generate build

generate:
	set -e
	go generate ./...

build:
	set -e
	$(foreach PACKAGE_INFO,$(BUILDABLE_PACKAGES), \
		$(eval ARTIFACT = $(word 1,$(subst :, ,$(PACKAGE_INFO)))) \
		$(eval PACKAGE_PATH = $(word 2,$(subst :, ,$(PACKAGE_INFO)))) \
		godep go build -ldflags "-X main.BuildTimeStr $(BUILD_DATE) -X main.BuildCommitHash $(BUILD_HASH)" -o $(ARTIFACT) $(PACKAGE_PATH) ; \
	)


clean:
	$(RM) $(foreach PACKAGE_INFO,$(BUILDABLE_PACKAGES), \
		$(eval ARTIFACT = $(word 1,$(subst :, ,$(PACKAGE_INFO)))) \
		$(ARTIFACT) \
	)

version.go

package main

import (
	"flag"
	"fmt"
	"io"
	"os"
	"strings"
	"time"
)

const (
	VERSION_MAJOR = "0.1"
	VERSION_MINOR = "0"

	ISO8601 = "2006-01-02T15:04:05-0700" // ISO-8601 date-time formatting string.
)

// Versioning detail information, set during build phase.
var (
	BuildTime       time.Time
	BuildTimeStr    string
	BuildCommitHash string
)

func init() {
	// Parse BuildTimeStr into BuildTime.
	if BuildTimeStr != "" {
		var err error
		if BuildTime, err = time.Parse(ISO8601, BuildTimeStr); err != nil {
			panic(fmt.Sprintf(`Parsing BuildTimeStr="%s" failed: %s`, BuildTimeStr, err))
		}
	}
	flag.Usage = func() {
		DisplayVersion(os.Stderr, "\n")
		fmt.Fprintln(os.Stderr, "usage:")
		flag.PrintDefaults()
	}
}

func DisplayVersion(writer io.Writer, delimiter string) {
	pieces := strings.Split(os.Args[0], "/")
	fmt.Fprintf(writer, "%s v%s.%s%s", pieces[len(pieces)-1], VERSION_MAJOR, VERSION_MINOR, delimiter)
	fmt.Fprintf(writer, "built on %s%s", BuildTime, delimiter)
	fmt.Fprintf(writer, "commit hash %s\n", BuildCommitHash)
}