From 45bad21f5fdf4fcd20b8bd8717b8e31fc66d119d Mon Sep 17 00:00:00 2001
From: Alex Eagle <alex@aspect.dev>
Date: Sun, 29 Oct 2023 13:28:09 +0100
Subject: [PATCH] feat(release): automate release archive and publish on GitHub
 Actions

---
 .github/workflows/release.yml     | 16 ++++++++++
 .github/workflows/release_prep.sh | 52 +++++++++++++++++++++++++++++++
 docs/CONTRIBUTING.md              | 10 ++++++
 version.bzl                       |  7 ++++-
 4 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 .github/workflows/release.yml
 create mode 100755 .github/workflows/release_prep.sh

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
new file mode 100644
index 0000000..a09207d
--- /dev/null
+++ b/.github/workflows/release.yml
@@ -0,0 +1,16 @@
+# Automatically perform a release whenever a new "release-like" tag is pushed to the repo.
+name: Release
+
+on:
+  push:
+    tags:
+      # Detect tags that look like a release.
+      # Note that we don't use a "v" prefix to help anchor this pattern.
+      # This is purely a matter of preference.
+      - "*.*.*"
+
+jobs:
+  release:
+    uses: bazel-contrib/.github/.github/workflows/release_ruleset.yaml@v5
+    with:
+      release_files: rules_license-*.tar.gz
diff --git a/.github/workflows/release_prep.sh b/.github/workflows/release_prep.sh
new file mode 100755
index 0000000..b29efcd
--- /dev/null
+++ b/.github/workflows/release_prep.sh
@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+
+set -o errexit -o nounset -o pipefail
+
+# Set by GH actions, see
+# https://docs.github.com/en/actions/learn-github-actions/environment-variables#default-environment-variables
+readonly TAG=${GITHUB_REF_NAME}
+# The prefix is chosen to match what GitHub generates for source archives.
+# This guarantees that users can easily switch from a released artifact to a source archive
+# with minimal differences in their code (e.g. strip_prefix remains the same)
+readonly PREFIX="rules_license-${TAG}"
+readonly ARCHIVE="rules_license-$TAG.tar.gz"
+
+# Configuration for 'git archive'
+# see https://git-scm.com/docs/git-archive/2.40.0#ATTRIBUTES
+cat >.git/info/attributes <<EOF
+# Omit folders that users don't need, making the distribution artifact smaller
+examples export-ignore
+
+# Substitution for the _VERSION placeholder in version.bzl
+version.bzl export-subst
+EOF
+
+git archive --format=tar --prefix=${PREFIX}/ ${TAG} | gzip > $ARCHIVE
+SHA=$(shasum -a 256 $ARCHIVE | awk '{print $1}')
+
+# The stdout of this program will be used as the top of the release notes for this release.
+cat << EOF
+## Using bzlmod with Bazel 6 or later:
+
+1. Add \`common --enable_bzlmod\` to \`.bazelrc\`.
+
+2. Add to your \`MODULE.bazel\` file:
+
+\`\`\`starlark
+bazel_dep(name = "rules_license", version = "${TAG}")
+\`\`\`
+
+## Using WORKSPACE:
+
+\`\`\`starlark
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+    name = "rules_license",
+    sha256 = "${SHA}",
+    strip_prefix = "${PREFIX}",
+    url = "https://github.com/bazelbuild/rules_license/releases/download/${TAG}/${ARCHIVE}",
+)
+\`\`\`starlark
+EOF
diff --git a/docs/CONTRIBUTING.md b/docs/CONTRIBUTING.md
index a5be947..71f7a72 100644
--- a/docs/CONTRIBUTING.md
+++ b/docs/CONTRIBUTING.md
@@ -31,3 +31,13 @@ implementation.
 
 This project follows
 [Google's Open Source Community Guidelines](https://opensource.google/conduct/).
+
+## Releasing
+
+To perform a release, simply tag the commit you wish to release, for example:
+
+```
+rules_license$ git fetch
+rules_license$ git tag 1.2.3 origin/main
+rules_license$ git push origin 1.2.3
+```
\ No newline at end of file
diff --git a/version.bzl b/version.bzl
index b2530e3..5241d01 100644
--- a/version.bzl
+++ b/version.bzl
@@ -13,4 +13,9 @@
 # limitations under the License.
 """The version of rules_license."""
 
-version = "0.0.7"
+# This is automagically replace by git during git archive using `git export-subst`
+# See https://git-scm.com/docs/git-archive/2.29.0#Documentation/git-archive.txt-export-subst
+_VERSION_PRIVATE = "$Format:%(describe:tags=true)$"
+
+# When using rules_license from source rather than from a release artifact, export a placeholder value
+version = "0.0.0-unreleased" if _VERSION_PRIVATE.startswith("$Format") else _VERSION_PRIVATE