v1.0.0: get version from git, or fail gracefully

.gitignore

@@ -1,3 +1,5 @@
+generated-version.go
+
 # ---> Go
 # Binaries for programs and plugins
 *.exe

README.md

@@ -1,3 +1,161 @@
 # git-version.go
 
-Use git tags to add semver to your go package.
+Use git tags to add semver to your go package.
+
+>     Goal: Either use an exact version like v1.0.0
+>           or translate the git version like v1.0.0-4-g0000000
+>           to a semver like v1.0.1-pre4+g0000000
+>
+>           Fail gracefully when git repo isn't available.
+
+# Demo
+
+```bash
+go run git.rootprojects.org/root/go-gitver
+```
+
+# QuickStart
+
+Add this to the top of your main file:
+
+```go
+//go:generate go run -mod=vendor git.rootprojects.org/root/go-gitver
+
+```
+
+Add a file that imports go-gitver (for versioning)
+
+```go
+// build +tools
+
+package example
+
+import _ "git.rootprojects.org/root/go-gitver"
+```
+
+Change you build instructions to be something like this:
+
+```bash
+go mod vendor
+go generate -mod=vendor ./...
+go build -mod=vendor -o example cmd/example/*.go
+```
+
+You don't have to use `mod vendor`, but I highly recommend it.
+
+# Options
+
+```
+version   print version and exit
+--fail    will cause non-zero exit status on failure
+```
+
+ENVs
+
+```
+# Alias for --fail
+GITVER_FAIL=true
+```
+
+For example:
+
+```go
+//go:generate go run -mod=vendor git.rootprojects.org/root/go-gitver --fail
+
+```
+
+```bash
+go run -mod=vendor git.rootprojects.org/root/go-gitver version
+```
+
+# Usage
+
+See `examples/basic`
+
+1. Create a `tools` package in your project
+2. Guard it against regular builds with `// build +tools`
+3. Include `_ "git.rootprojects.org/root/go-gitver"` in the imports
+4. Declare `var GitRev, GitVersion, GitTimestamp string` in your `package main`
+5. Include `//go:generate go run -mod=vendor git.rootprojects.org/root/go-gitver` as well
+
+`tools/tools.go`:
+
+```go
+// build +tools
+
+// This is a dummy package for build tooling
+package tools
+
+import (
+	_ "git.rootprojects.org/root/go-gitver"
+)
+```
+
+`main.go`:
+
+```go
+//go:generate go run git.rootprojects.org/root/go-gitver --fail
+
+package main
+
+import "fmt"
+
+var (
+	GitRev       = "0000000"
+	GitVersion   = "v0.0.0-pre0+0000000"
+	GitTimestamp = "0000-00-00T00:00:00+0000"
+)
+
+func main() {
+  fmt.Println(GitRev)
+  fmt.Println(GitVersion)
+  fmt.Println(GitTimestamp)
+}
+```
+
+If you're using `go mod vendor` (which I highly recommend that you do),
+you'd modify the `go:generate` ever so slightly:
+
+```go
+//go:generate go run -mod=vendor git.rootprojects.org/root/go-gitver --fail
+```
+
+The only reason I didn't do that in the example is that I'd be included
+the repository in itself and that would be... weird.
+
+# Why a tools package?
+
+>     import "git.rootprojects.org/root/go-gitver" is a program, not an importable package
+
+Having a tools package with a build tag that you don't use is a nice way to add exact
+versions of a command package used for tooling to your `go.mod` with `go mod tidy`,
+without getting the error above.
+
+# git: behind the curtain
+
+These are the commands that are used under the hood to produce the versions.
+
+Shows the git tag + description. Assumes that you're using the semver format `v1.0.0` for your base tags.
+
+```bash
+git describe --tags --dirty --always
+# v1.0.0
+# v1.0.0-1-g0000000
+# v1.0.0-dirty
+```
+
+Show the commit date (when the commit made it into the current tree).
+Internally we use the current date when the working tree is dirty.
+
+```bash
+git show v1.0.0-1-g0000000 --format=%cd --date=format:%Y-%m-%dT%H:%M:%SZ%z --no-patch
+# 2010-01-01T20:30:00Z-0600
+# fatal: ambiguous argument 'v1.0.0-1-g0000000-dirty': unknown revision or path not in the working tree.
+```
+
+Shows the most recent commit.
+
+```bash
+git rev-parse HEAD
+# 0000000000000000000000000000000000000000
+```

examples/basic/README.md

@@ -0,0 +1,30 @@
+# Example
+
+Prints the version or a nice message
+
+# Build
+
+Typically the developer would perform these steps
+and then commit the results (`go.mod`, `go.sum`, `vendor`).
+
+However, since this is an example within the project directory,
+that seemed a little redundant.
+
+```bash
+go mod tidy
+go mod vendor
+```
+
+These are the instructions that someone cloning the repo might use.
+
+```bash
+go generate -mod=vendor ./...
+go build -mod=vendor -o hello *.go
+```
+
+Note: If the source is distributed in a non-git tarball then
+`generated-version.go` will not be output, and whatever
+version info is in `package main` will remain as-is.
+
+If you would prefer the build process to fail (i.e. in a CI/CD pipeline),
+you can set the environment variable `GITVER_FAIL=true`.

examples/basic/go.mod

@@ -0,0 +1,3 @@
+module example.com/hello
+
+go 1.12

examples/basic/main.go

@@ -0,0 +1,28 @@
+//go:generate go run -mod=vendor git.rootprojects.org/root/go-gitver --fail
+
+package main
+
+import (
+	"flag"
+	"fmt"
+)
+
+var (
+	GitRev       = "0000000"
+	GitVersion   = "v0.0.0-pre0+0000000"
+	GitTimestamp = "0000-00-00T00:00:00+0000"
+)
+
+func main() {
+	showVersion := flag.Bool("version", false, "Print version and exit")
+	flag.Parse()
+
+	if *showVersion {
+		fmt.Println(GitRev)
+		fmt.Println(GitVersion)
+		fmt.Println(GitTimestamp)
+		return
+	}
+
+	fmt.Println("Hello, World!")
+}

examples/basic/tools/tools.go

@@ -0,0 +1,8 @@
+// build +tools
+
+// This is a dummy package for build tooling
+package tools
+
+import (
+	_ "git.rootprojects.org/root/go-gitver"
+)

gitver.go

@@ -0,0 +1,207 @@
+//go:generate go run -mod=vendor git.rootprojects.org/root/go-gitver
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"log"
+	"os"
+	"os/exec"
+	"regexp"
+	"strconv"
+	"strings"
+	"text/template"
+	"time"
+)
+
+var exitCode int
+var exactVer *regexp.Regexp
+var gitVer *regexp.Regexp
+var verFile = "generated-version.go"
+
+var (
+	GitRev       = "0000000"
+	GitVersion   = "v0.0.0-pre0+g0000000"
+	GitTimestamp = "0000-00-00T00:00:00+0000"
+)
+
+func init() {
+	// exactly vX.Y.Z (go-compatible semver)
+	exactVer = regexp.MustCompile(`^v\d+\.\d+\.\d+$`)
+
+	// vX.Y.Z-n-g0000000 git post-release, semver prerelease
+	// vX.Y.Z-dirty git post-release, semver prerelease
+	gitVer = regexp.MustCompile(`^(v\d+\.\d+)\.(\d+)(-(\d+))?(-(g[0-9a-f]+))?(-(dirty))?`)
+}
+
+func main() {
+	args := os.Args[1:]
+	for i := range args {
+		arg := args[i]
+		if "-f" == arg || "--fail" == arg {
+			exitCode = 1
+		} else if "-V" == arg || "version" == arg || "-version" == arg || "--version" == arg {
+			fmt.Println(GitRev)
+			fmt.Println(GitVersion)
+			fmt.Println(GitTimestamp)
+			os.Exit(0)
+		}
+	}
+	if "" != os.Getenv("GITVER_FAIL") && "false" != os.Getenv("GITVER_FAIL") {
+		exitCode = 1
+	}
+
+	desc, err := gitDesc()
+	if nil != err {
+		log.Fatalf("Failed to get git version: %s\n", err)
+		os.Exit(exitCode)
+	}
+	rev := gitRev()
+	ver := semVer(desc)
+	ts, err := gitTimestamp(desc)
+	if nil != err {
+		ts = time.Now()
+	}
+
+	v := struct {
+		Timestamp string
+		Version   string
+		GitRev    string
+	}{
+		Timestamp: ts.Format(time.RFC3339),
+		Version:   ver,
+		GitRev:    rev,
+	}
+
+	// Create or overwrite the go file from template
+	var buf bytes.Buffer
+	if err := versionTpl.Execute(&buf, v); nil != err {
+		panic(err)
+	}
+
+	// Format
+	src, err := format.Source(buf.Bytes())
+	if nil != err {
+		panic(err)
+	}
+
+	// Write to disk (in the Current Working Directory)
+	f, err := os.Create(verFile)
+	if nil != err {
+		panic(err)
+	}
+	if _, err := f.Write(src); nil != err {
+		panic(err)
+	}
+	if err := f.Close(); nil != err {
+		panic(err)
+	}
+}
+
+func gitDesc() (string, error) {
+	args := strings.Split("git describe --tags --dirty --always", " ")
+	cmd := exec.Command(args[0], args[1:]...)
+	out, err := cmd.CombinedOutput()
+	if nil != err {
+		// Don't panic, just carry on
+		//out = []byte("v0.0.0-0-g0000000")
+		return "", err
+	}
+	return strings.TrimSpace(string(out)), nil
+}
+
+func gitRev() string {
+	args := strings.Split("git rev-parse HEAD", " ")
+	cmd := exec.Command(args[0], args[1:]...)
+	out, err := cmd.CombinedOutput()
+	if nil != err {
+		fmt.Fprintf(os.Stderr,
+			"\nUnexpected Error\n\n"+
+				"Please open an issue at https://git.rootprojects.org/root/go-gitver/issues/new \n"+
+				"Please include the following:\n\n"+
+				"Command: %s\n"+
+				"Output: %s\n"+
+				"Error: %s\n"+
+				"\nPlease and Thank You.\n\n", strings.Join(args, " "), out, err)
+		os.Exit(exitCode)
+	}
+	return strings.TrimSpace(string(out))
+}
+
+func semVer(desc string) string {
+	if exactVer.MatchString(desc) {
+		// v1.0.0
+		return desc
+	}
+
+	if !gitVer.MatchString(desc) {
+		return ""
+	}
+
+	// (v1.0).(0)(-(1))(-(g0000000))(-(dirty))
+	vers := gitVer.FindStringSubmatch(desc)
+	patch, err := strconv.Atoi(vers[2])
+	if nil != err {
+		fmt.Fprintf(os.Stderr,
+			"\nUnexpected Error\n\n"+
+				"Please open an issue at https://git.rootprojects.org/root/go-gitver/issues/new \n"+
+				"Please include the following:\n\n"+
+				"git description: %s\n"+
+				"RegExp: %#v\n"+
+				"Error: %s\n"+
+				"\nPlease and Thank You.\n\n", desc, gitVer, err)
+		os.Exit(exitCode)
+	}
+
+	// v1.0.1-pre1
+	// v1.0.1-pre1+g0000000
+	// v1.0.1-pre0+dirty
+	// v1.0.1-pre0+g0000000-dirty
+	if "" == vers[4] {
+		vers[4] = "0"
+	}
+	ver := fmt.Sprintf("%s.%d-pre%s", vers[1], patch+1, vers[4])
+	if "" != vers[6] || "dirty" == vers[8] {
+		ver += "+"
+		if "" != vers[6] {
+			ver += vers[6]
+			if "" != vers[8] {
+				ver += "-"
+			}
+		}
+		ver += vers[8]
+	}
+
+	return ver
+}
+
+func gitTimestamp(desc string) (time.Time, error) {
+	args := []string{
+		"git",
+		"show", desc,
+		"--format=%cd",
+		"--date=format:%Y-%m-%dT%H:%M:%SZ%z",
+		"--no-patch",
+	}
+	cmd := exec.Command(args[0], args[1:]...)
+	out, err := cmd.CombinedOutput()
+	if nil != err {
+		// a dirty desc was probably used
+		return time.Time{}, err
+	}
+	return time.Parse(time.RFC3339, strings.TrimSpace(string(out)))
+}
+
+var versionTpl = template.Must(template.New("").Parse(`// Code generated by go generate; DO NOT EDIT.
+package main
+
+func init() {
+	GitRev = "{{ .GitRev }}"
+	if "" != "{{ .Version }}" {
+		GitVersion = "{{ .Version }}"
+	}
+	GitTimestamp = "{{ .Timestamp }}"
+}
+`))

go.mod

@@ -0,0 +1,3 @@
+module git.rootprojects.org/root/go-gitver
+
+go 1.12