include source repo, revision and go package version as build-args

Signed-off-by: Avi Deitcher <avi@deitcher.net>

src/cmd/linuxkit/pkglib/build.go

@@ -309,12 +309,23 @@ func (p Pkg) Build(bos ...BuildOpt) error {
 		if p.git != nil && p.gitRepo != "" {
 			imageBuildOpts.Labels["org.opencontainers.image.source"] = p.gitRepo
 		}
-		if p.git != nil && !p.dirty {
-			commit, err := p.git.commitHash("HEAD")
+		var (
+			gitCommit    string
+			goPkgVersion string
+		)
+		if p.git != nil {
+			if !p.dirty {
+				gitCommit, err = p.git.commitHash("HEAD")
+				if err != nil {
+					return err
+				}
+				imageBuildOpts.Labels["org.opencontainers.image.revision"] = gitCommit
+			}
+			// get the go version or pseudo-version
+			goPkgVersion, err = p.git.goPkgVersion()
 			if err != nil {
 				return err
 			}
-			imageBuildOpts.Labels["org.opencontainers.image.revision"] = commit
 		}
 
 		imageBuildOpts.NetworkMode = "default"
@@ -342,6 +353,16 @@ func (p Pkg) Build(bos ...BuildOpt) error {
 				imageBuildOpts.BuildArgs[parts[0]] = &parts[1]
 			}
 		}
+		// add in information about the build process that might be useful
+		if _, ok := imageBuildOpts.BuildArgs["SOURCE"]; !ok && p.gitRepo != "" {
+			imageBuildOpts.BuildArgs["SOURCE"] = &p.gitRepo
+		}
+		if _, ok := imageBuildOpts.BuildArgs["REVISION"]; !ok && gitCommit != "" {
+			imageBuildOpts.BuildArgs["REVISION"] = &gitCommit
+		}
+		if _, ok := imageBuildOpts.BuildArgs["GOPKGVERSION"]; !ok && goPkgVersion != "" {
+			imageBuildOpts.BuildArgs["GOPKGVERSION"] = &goPkgVersion
+		}
 
 		// build for each arch and save in the linuxkit cache
 		for _, platform := range platformsToBuild {

src/cmd/linuxkit/pkglib/git.go

@@ -211,3 +211,36 @@ func (g git) isDirty(pkg, commit string) (bool, error) {
 		return false, err
 	}
 }
+
+// goPkgVersion return a version that is compliant with go package versioning.
+// This would either be:
+//
+// - The tag name if the most recent commit is tagged
+// - The structure <version>-<count>-<commmit> if the most recent commit is not tagged
+//
+// See https://go.dev/ref/mod for more information
+func (g git) goPkgVersion() (string, error) {
+	lastSemver, _ := g.commandStdout(nil, "--no-pager", "describe", "--match='v[0-9].[0-9].[0-9]*'", "--abbrev=0", "--tags")
+	if lastSemver == "" {
+		lastSemver = "v0.0.0"
+	}
+	commitList := "HEAD"
+	if lastSemver != "v0.0.0" {
+		commitList = fmt.Sprintf("%s..HEAD", lastSemver)
+	}
+	count, err := g.commandStdout(nil, "rev-list", commitList, "--count")
+	if err != nil {
+		return "", err
+	}
+	version := ""
+	if count == "0" {
+		version = lastSemver
+	} else {
+		dateCommit, err := g.commandStdout(nil, "--no-pager", "show", "--quiet", "--abbrev=12", "--date=format-local:%Y%m%d%H%M%S", "--format=%cd-%h")
+		if err != nil {
+			return "", err
+		}
+		version = fmt.Sprintf("%s-%s", lastSemver, dateCommit)
+	}
+	return version, nil
+}