cmd/containerbuild: set container build timestamp to the timestamp of the commit (#15)

Signed-off-by: Xe Iaso <me@xeiaso.net>

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- Docker images are now built with the timestamp set to the commit timestamp
 - The README now points to TecharoHQ/anubis instead of Xe/x
 - Images are built using ko instead of `docker buildx build`
   [#13](https://github.com/TecharoHQ/anubis/pull/13)

cmd/containerbuild/main.go

@@ -30,14 +30,24 @@ func main() {
 
 	koDockerRepo := strings.TrimRight(*dockerRepo, "/"+filepath.Base(*dockerRepo))
 	version, err := run("git describe --tags --always --dirty")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	commitTimestamp, err := run("git log -1 --format='%ct'")
+	if err != nil {
+		log.Fatal(err)
+	}
 
 	slog.Debug(
 		"ko env",
 		"KO_DOCKER_REPO", koDockerRepo,
+		"SOURCE_DATE_EPOCH", commitTimestamp,
 		"VERSION", version,
 	)
 
 	os.Setenv("KO_DOCKER_REPO", koDockerRepo)
+	os.Setenv("SOURCE_DATE_EPOCH", commitTimestamp)
 	os.Setenv("VERSION", version)
 
 	setOutput("version", version)