Update readme and add scheduled trigger (#4)

* Add readme and add scheduled trigger

* Fix cli

Author: ryanking13

.github/workflows/build.yml

@@ -2,9 +2,13 @@ name: Build Cross-build environment for pyodide-build
 
 on:
   pull_request:
+  push:
+    branches:
+      - main
   workflow_dispatch:
-  release:
-    types: [published]
+  schedule:
+    # Run at 00:00 UTC on the 1st, 10th, and 20th of every month
+    - cron: '0 0 1,10,20 * *'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
@@ -96,8 +100,8 @@ jobs:
     needs: [build]
     if: >-
       github.repository == 'pyodide/pyodide-build-environment-nightly' &&
-      github.event_name == 'release' &&
-      github.event.action == 'published'
+      (github.event_name == 'push' && startsWith(github.ref, 'refs/tags')) ||
+      (github.event_name == 'schedule')
     permissions:
       # Required to sign the attestations
       id-token: write
@@ -116,6 +120,18 @@ jobs:
         with:
           subject-path: |
             dist/xbuildenv.tar.bz
+      
+      - name: Calc release version
+        id: release_version
+        shell: bash
+        run: |
+          if [[ ${{ github.event_name }} == 'schedule' ]]; then
+            echo "release_version=$(date +'%Y%m%d')" >> $GITHUB_OUTPUT
+          else
+            echo "release_version=${{ github.ref }}" >> $GITHUB_OUTPUT
+          fi
+
+          cat $GITHUB_OUTPUT
 
       - name: Verify them, to ensure that the wheels they were attested correctly
         env:
@@ -126,12 +142,8 @@ jobs:
 
       - name: Create GitHub release with these wheels
         uses: softprops/action-gh-release@01570a1f39cb168c169c802c3bceb9e93fb10974 # v2.1.0
-        if: >-
-          github.repository == 'pyodide/pyodide-build-environment-nightly' &&
-          github.event_name == 'release' &&
-          github.event.action == 'published'
         with:
           files: |
             dist/*.tar.bz
           fail_on_unmatched_files: true
-          name: Pyodide cross-build environment
+          name: ${{ steps.release_version.outputs.release_version }}

README.md

@@ -1,2 +1,28 @@
 # pyodide-build-environment-nightly
+
 Nightly cross build environments for building Pyodide packages
+
+## Usage
+
+This repository contains nightly cross build environments for building Pyodide packages.
+The target user of this repository is package maintainers who want to build their packages against the unreleased version of Pyodide.
+
+Each release in this repository contains a tip-of-tree build of Pyodide of the given date.
+You can use the `pyodide xbuildenv install` command to install the build environment for a given date.
+
+```bash
+pip install pyodide-build
+
+# Change the date to the date of the build you want to use
+pyodide xbuildenv install --url "https://github.com/pyodide/pyodide-build-environment-nightly/releases/download/20250125/xbuildenv.tar.bz"
+
+# Now you can use the build environment to build your package
+pyodide build
+```
+
+## Maintainer Notes
+
+The build environment is periodically built and released by GHA.
+
+Otherwise, if you want to manually trigger a build, you can create a new tag.
+Creating a tag will trigger a GHA workflow that builds the cross build environment and uploads it as a release asset.