add tag-releases script

ci/tag-releases.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+#
+# Creates a new git tag for each package that has a new version.
+
+set -e
+
+source ci/detect-changed-manifests.sh
+
+changed_manifests=$(detect_changed_manifests)
+
+if [ -n "$changed_manifests" ]; then
+  for manifest_path in $changed_manifests; do
+    # Read the package name and version from its manifest.
+    package_name=$(grep '^name\s*=' "$manifest_path" | awk -F'\"' '{print $2}')
+    new_version=$(grep '^version\s*=' "$manifest_path" | awk -F'\"' '{print $2}')
+
+    # Create a new git tag.
+    tag_name="${package_name}-v${new_version}"
+    git tag "$tag_name"
+    echo "Created tag: $tag_name"
+  done
+else
+  echo "No versions changed."
+fi