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package main
import (
"flag"
"io"
"log"
"os"
"os/exec"
"path/filepath"
"strings"
"text/template"
"time"
)
var (
flPackageName = flag.String("package", "version", "name for the generated golang package")
flVariableName = flag.String("variable", "VERSION", "variable name in the generated golang package")
flOutputFile = flag.String("output", "", "output filename (default stdout)")
)
func main() {
flag.Parse()
dir := "."
if flag.NArg() > 0 {
dir = flag.Args()[0]
}
dir, err := filepath.Abs(dir)
if err != nil {
log.Fatal(err)
}
var output io.Writer
if len(*flOutputFile) > 0 {
fh, err := os.Create(*flOutputFile)
if err != nil {
log.Fatal(err)
}
defer fh.Close()
output = fh
} else {
output = os.Stdout
}
vers, err := GitDescribe(dir)
if err != nil {
log.Fatal(err)
}
vp := VersionPackage{
Name: *flPackageName,
Path: dir,
Date: time.Now(),
Variable: *flVariableName,
Version: vers,
}
packageTemplate.Execute(output, vp)
}
// VersionPackage is the needed information to template a version package
type VersionPackage struct {
Name string
Path string
Date time.Time
Variable string
Version string
}
var packageTemplate = template.Must(template.New("default").Parse(packageLayout))
var packageLayout = `package {{.Name}}
// AUTO-GENERATED. DO NOT EDIT
// {{.Date}}
// {{.Variable}} is generated by git-describe from gen.go
var {{.Variable}} = "{{.Version}}"
`
// GitDescribe calls `git describe` in the provided path
func GitDescribe(path string) (string, error) {
cwd, err := os.Getwd()
if err != nil {
return "", err
}
// TODO check if this is a directory
if err := os.Chdir(path); err != nil {
return "", err
}
defer os.Chdir(cwd)
buf, err := exec.Command("git", "describe").CombinedOutput()
if err != nil {
return "", err
}
return strings.TrimSpace(string(buf)), nil
}
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