main: --version includes git commit

Include the commit of the build (if available in the build environment),
also include the version of `images` in the build; if available.

Signed-off-by: Simon de Vlieger <supakeen@redhat.com>

cmd/image-builder/main.go

@@ -28,9 +28,8 @@ import (
 )
 
 var (
-	osStdout     io.Writer = os.Stdout
-	osStderr     io.Writer = os.Stderr
-	BuildVersion           = "DEVEL"
+	osStdout io.Writer = os.Stdout
+	osStderr io.Writer = os.Stderr
 )
 
 // basenameFor returns the basename for directory and filenames
@@ -423,11 +422,13 @@ image-type and blueprint.
 Image-builder builds operating system images for a range of predefined
 operating systems like Fedora, CentOS and RHEL with easy customizations support.`,
 		SilenceErrors: true,
-		Version:       BuildVersion,
+		Version:       prettyVersion(),
 		CompletionOptions: cobra.CompletionOptions{
 			HiddenDefaultCmd: true,
 		},
 	}
+	rootCmd.SetVersionTemplate(prettyVersion())
+
 	rootCmd.PersistentFlags().String("data-dir", "", `Override the default data directory for e.g. custom repositories/*.json data`)
 	rootCmd.PersistentFlags().StringArray("extra-repo", nil, `Add an extra repository during build (will *not* be gpg checked and not be part of the final image)`)
 	rootCmd.PersistentFlags().StringArray("force-repo", nil, `Override the base repositories during build (these will not be part of the final image)`)

cmd/image-builder/version.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"runtime/debug"
+	"strings"
+
+	"gopkg.in/yaml.v3"
+)
+
+// Usually set by whatever is building the binary with a `-x main.version=22`, for example
+// in `make build`.
+var version = "unknown"
+
+type versionDescription struct {
+	ImageBuilder struct {
+		Version      string `yaml:"version"`
+		Commit       string `yaml:"commit"`
+		Dependencies struct {
+			Images string `yaml:"images"`
+		} `yaml:"dependencies"`
+	} `yaml:"image-builder"`
+}
+
+func readVersionFromBinary() *versionDescription {
+	// We'll be getting these values from the build info if they're available, otherwise
+	// they will always be set to unknown. Note that `version` is set globally so it can
+	// be defined by whatever is building this project.
+	commit := "unknown"
+	images := "unknown"
+
+	if bi, ok := debug.ReadBuildInfo(); ok {
+		for _, bs := range bi.Settings {
+			switch bs.Key {
+			case "vcs.revision":
+				commit = bs.Value
+			}
+		}
+
+		for _, dep := range bi.Deps {
+			if dep.Path == "github.com/osbuild/images" {
+				images = dep.Version
+			}
+		}
+	}
+
+	vd := &versionDescription{}
+
+	vd.ImageBuilder.Version = version
+	vd.ImageBuilder.Commit = commit
+
+	vd.ImageBuilder.Dependencies.Images = images
+
+	return vd
+}
+
+func prettyVersion() string {
+	var b strings.Builder
+
+	enc := yaml.NewEncoder(&b)
+	enc.SetIndent(2)
+
+	enc.Encode(readVersionFromBinary())
+
+	return b.String()
+}