WIP, nae nae

.gitignore

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

README.md

@@ -1,3 +1,71 @@
 # 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
+```
+
+# 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 -mod=vendor git.rootprojects.org/root/go-gitver
+
+package main
+
+import "fmt"
+
+var (
+  GitRev = "0000000"
+  GitVersion = "v0.0.0-pre0+g0000000"
+  GitTimestamp = "0000-00-00T00:00:00+0000"
+)
+
+func main() {
+  fmt.Println(GitRev)
+  fmt.Println(GitVersion)
+  fmt.Println(GitTimestamp)
+}
+```
+
+# Behind the curtain
+
+```bash
+git describe --tags --dirty --always
+# v1.0.0
+# v1.0.0-1
+
+git log --format='format:%cI' -n 1 --since=(git describe --tags --dirty --always)
+git rev-parse HEAD
+```

examples/basic/main.go

@@ -0,0 +1,17 @@
+//go:generate go run -mod=vendor git.rootprojects.org/root/go-gitver
+
+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)
+}

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 +1,166 @@
+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"
+
+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+)-)?(dirty|g)`)
+}
+
+func main() {
+	args := os.Args[1:]
+	for i := range args {
+		arg := args[i]
+		if "-f" == arg || "--fail" == arg {
+			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 {
+		fmt.Println("badtimes", err) // TODO remove
+		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 {
+	var ver string
+	if exactVer.MatchString(desc) {
+		// v1.0.0
+		ver = desc
+	} else if gitVer.MatchString(desc) {
+		// ((v1.0).(0)-(1))
+		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
+		ver = fmt.Sprintf("%s.%d-pre%s", vers[1], patch+1, vers[4])
+	}
+	return ver
+}
+
+func gitTimestamp(desc string) (time.Time, error) {
+	args := strings.Split(fmt.Sprintf("git show %s --format='format:%%cI' --no-patch", desc), " ")
+	cmd := exec.Command(args[0], args[1:]...)
+	out, err := cmd.CombinedOutput()
+	fmt.Printf("foo:\n%#v\n", args)
+	fmt.Printf("bar:\n%s\n", strings.Join(args, " "))
+	fmt.Println("baz:\n", string(out), err)
+	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 }}"
+	GitVersion = "{{ .Version }}"
+	GitTimestamp = "{{ .Timestamp }}"
+}
+`))