flatpak-builder: Add the git commit as the ostree commit subject

Author: alatiera

flatpak-builder/index.js

@@ -222,6 +222,7 @@ const build = async (manifest, manifestPath, cacheHitKey, config) => {
     `--repo=${config.localRepoName}`,
     '--disable-rofiles-fuse',
     `--install-deps-from=${config.repositoryName}`,
+    `--subject=${github.context.sha}`,
     '--force-clean',
     `--default-branch=${branch}`,
     `--arch=${config.arch}`