Staged publishing support

publish/README.md

@@ -1,3 +1,24 @@
 # changesets/action/publish
 
-TODO
+Publishes packages with Changesets.
+
+Set the optional `stage` input to `true` or `false` to override
+`stagedPublishing` from the Changesets config. The input is tri-state: omitting
+it leaves the config in control. An explicit `stage` cannot be combined with a
+custom `script`; configure the script itself instead.
+
+When packages are staged, the action uploads a 30-day handoff and returns its
+exact id as `staged-release-artifact-id`. It also prints a topologically
+ordered approval command:
+
+```sh
+changeset stage approve <id...>
+```
+
+That command is only a convenience and uses the default registry. For custom
+or multiple registries, split the IDs into correctly scoped commands and pass
+`--registry` to each.
+
+After approval, pass the artifact id to
+`changesets/action/github-release` to verify publication and create Git tags
+and GitHub Releases.

publish/action.yml

@@ -11,6 +11,12 @@ inputs:
   script:
     description: "The command to use to publish packages"
     required: false
+  stage:
+    description: >
+      Whether to use staged publishing. Omit to use the Changesets config,
+      set to true for --stage, or false for --no-stage. Cannot be combined
+      with a custom script.
+    required: false
   pack-dir-artifact-id:
     description: "Artifact id for packed publish output generated by the pack subaction"
     required: false
@@ -30,6 +36,8 @@ outputs:
   published-packages:
     description: >
       A JSON array to present the published packages. The format is `[{"name": "@xx/xx", "version": "1.2.0"}, {"name": "@xx/xy", "version": "0.8.9"}]`
+  staged-release-artifact-id:
+    description: "Artifact id for the staged release handoff"
 branding:
   icon: package
   color: blue