ci, docs: rebuild on awesome-gbdev changes, add CONTRIBUTING.md (#8)

CI:
- Run the deploy workflow on an `awesome-gbdev-updated` repository_dispatch
  event, sent by awesome-gbdev when its README changes, and on manual
  workflow_dispatch.
- Serialize deploys with a concurrency group, so a push and a dispatch
  can't push to master at the same time.
- Skip the deploy commit when the build output is unchanged, instead of
  failing on an empty commit.

Docs:
- Move the resources page instructions from README.md to a new
  CONTRIBUTING.md, linked from the README.
- Document when the website is deployed and the token awesome-gbdev uses
  to trigger the deploy, pointing to awesome-gbdev's CONTRIBUTING.md for
  the sending side.

Author: avivace

.github/workflows/deploy.yml

@@ -3,6 +3,15 @@ name: CI
 on:
   push:
     branches: [ dev ]
+  # Sent by awesome-gbdev when its README changes, to rebuild the resources page
+  repository_dispatch:
+    types: [ awesome-gbdev-updated ]
+  workflow_dispatch:
+
+# Don't let two deploys push to master at the same time
+concurrency:
+  group: deploy
+  cancel-in-progress: false
 
 jobs:
   build:
@@ -67,5 +76,9 @@ jobs:
         git remote -v
         git branch -v
         git add -A
-        git commit -am 'Update build'
+        if git diff --cached --quiet; then
+          echo "Build output unchanged, nothing to deploy."
+          exit 0
+        fi
+        git commit -m 'Update build'
         git push -v

CONTRIBUTING.md

@@ -0,0 +1,32 @@
+# Contributing
+
+## Resources page
+
+`website/resources.md` (served at [gbdev.io/resources](https://gbdev.io/resources)) is not committed: it's generated from the [awesome-gbdev](https://github.com/gbdev/awesome-gbdev) README by `yarn build-resources`. The website-only top of the page (front matter, videos, notes) lives in [`scripts/resources/header.md`](scripts/resources/header.md), and everything between the `<!-- gbdev.io:begin body -->` and `<!-- gbdev.io:end body -->` markers of the awesome-gbdev README is appended to it.
+
+By default the README is fetched from the master branch of awesome-gbdev. Run this before `yarn dev`, and again whenever you want to pull in changes to the list (requires Node 18 or later):
+
+```bash
+# From the master branch of awesome-gbdev
+yarn build-resources
+
+# From a specific branch, tag or commit
+yarn build-resources 0c457e7833cd22985976dc0eecc859919ae589b0
+
+# From a local copy of the README (e.g. to preview changes to the list md)
+yarn build-resources ../awesome-gbdev/README.md
+```
+
+`yarn build` runs `yarn build-resources` automatically before building. By default (when `RESOURCES_MD_SRC` is not set) the script fetches the README from the master branch of awesome-gbdev on GitHub by itself, so deployed builds always use the current list. To build from another source instead, set the `RESOURCES_MD_SRC` environment variable to any of the values accepted by `yarn build-resources` (a branch, tag, commit or local path):
+
+```bash
+# Fetches the README from awesome-gbdev master
+yarn build
+
+# Uses a local copy of the README instead
+RESOURCES_MD_SRC=../awesome-gbdev/README.md yarn build
+```
+
+## CI
+
+The website is rebuilt and deployed on every push to `dev`, and also whenever the awesome-gbdev README changes: awesome-gbdev sends an `awesome-gbdev-updated` [`repository_dispatch`](https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows#repository_dispatch) event to this repository, which runs the deploy workflow. To do so, awesome-gbdev holds a fine-grained token with access to this repository (Contents: read and write): if it expires or is revoked, the resources page stops updating until the next push here. How the event is sent is documented in the [awesome-gbdev CONTRIBUTING.md](https://github.com/gbdev/awesome-gbdev/blob/master/CONTRIBUTING.md). A deploy may also be started manually from the Actions tab ("Run workflow").

README.md

@@ -18,29 +18,4 @@ yarn dev
 yarn build
 ```
 
-## Resources page
-
-`website/resources.md` (served at [gbdev.io/resources](https://gbdev.io/resources)) is not committed: it's generated from the [awesome-gbdev](https://github.com/gbdev/awesome-gbdev) README by `yarn build-resources`. The website-only top of the page (front matter, videos, notes) lives in [`scripts/resources/header.md`](scripts/resources/header.md), and everything between the `<!-- gbdev.io:begin body -->` and `<!-- gbdev.io:end body -->` markers of the awesome-gbdev README is appended to it.
-
-By default the README is fetched from the master branch of awesome-gbdev. Run this before `yarn dev`, and again whenever you want to pull in changes to the list (requires Node 18 or later):
-
-```bash
-# From the master branch of awesome-gbdev
-yarn build-resources
-
-# From a specific branch, tag or commit
-yarn build-resources 0c457e7833cd22985976dc0eecc859919ae589b0
-
-# From a local copy of the README (e.g. to preview changes to the list md)
-yarn build-resources ../awesome-gbdev/README.md
-```
-
-`yarn build` runs `yarn build-resources` automatically before building. By default (when `RESOURCES_MD_SRC` is not set) the script fetches the README from the master branch of awesome-gbdev on GitHub by itself, so deployed builds always use the current list. To build from another source instead, set the `RESOURCES_MD_SRC` environment variable to any of the values accepted by `yarn build-resources` (a branch, tag, commit or local path):
-
-```bash
-# Fetches the README from awesome-gbdev master
-yarn build
-
-# Uses a local copy of the README instead
-RESOURCES_MD_SRC=../awesome-gbdev/README.md yarn build
-```
+See [CONTRIBUTING.md](CONTRIBUTING.md) to learn how to contribute to the website, including how the resources page is generated.