docs: developer guide to the Forgejo runner

# Conflicts:
#	developer/forgejo-runner.md

developer/forgejo-runner.md

@@ -0,0 +1,101 @@
+---
+layout: '~/layouts/Markdown.astro'
+title: Forgejo runner implementation notes
+license: 'CC-BY-SA-4.0'
+---
+
+The [Forgejo runner](https://codeberg.org/forgejo/runner) depends on [a fork of ACT](https://code.forgejo.org/forgejo/act) and is a dependency of the [setup-forgejo action](https://code.forgejo.org/actions/setup-forgejo). Together they provide a development environment with end to end testing. Each repository also has some unit testing that can be used to quickly detect the simplest mistakes such as a failure to compile or static code checking failures (vulnerability, lint, etc.).
+
+# Forgejo runner
+
+Assuming the modifications to the [Forgejo runner](https://codeberg.org/forgejo/runner) are pushed to a fork in a branch named `wip-runner-change`, a pull request will verify it compiles and the binary is sane (running `forgejo-runner --version`). It will not verify that it is able to properly run jobs when connected to a live Forgejo instance.
+
+For end to end testing, a branch should be pushed to a fork of the [setup-forgejo action](https://code.forgejo.org/actions/setup-forgejo) with a [modification to the tests](https://code.forgejo.org/actions/setup-forgejo/src/commit/ae7f03683b7b05c7d9c6aaeacaf27843de0366a4/.forgejo/workflows/integration.yml#L10-L19), similar to:
+
+```yaml
+#
+# Uncomment the following for a shortcut to debugging the Forgejo runner.
+# It will build the runner from a designated repository and branch instead of
+# downloading it from a canonical release.
+#
+./forgejo-test-helper.sh build_runner https://code.forgejo.org/earl-warren/runner wip-runner-change
+```
+
+Where https://code.forgejo.org/earl-warren/runner is the URL of the Forgejo runner fork and `wip-runner-change` is the branch where the changes under test were pushed. When they do the `setup-forgejo` branch can be discarded.
+
+The runner can be released by merging the `wip-runner-change` branch and by pushing a new tag, for instance `v10.2.3`. Once published, the `setup-forgejo` action can be updated to default to this latest version knowing it already passed integration tests.
+
+# ACT
+
+Assuming the modifications to [ACT](https://code.forgejo.org/forgejo/act) are pushed to a fork in a branch named `wip-act-change`, a pull request will verify it compiles. It will not verify that the Forgejo runner can compile with it.
+
+For verifying it is compatible with the Forgejo runner, a branch should be pushed to a fork of the [Forgejo runner](https://codeberg.org/forgejo/runner) (for instance `wip-runner-change`) that uses the ACT version under test in the `wip-act-change` by modifying `go.mod` to contain something like the following and running `go mod tidy`:
+
+```
+replace github.com/nektos/act => code.forgejo.org/earl-warren/act wip-act-change
+```
+
+Where https://code.forgejo.org/earl-warren/act is the URL of the act fork and `wip-act-change` is the branch where the changes under test were pushed. It will not verify that it is able to properly run jobs when connected to a live Forgejo instance. The `wip-runner-change` branch must, in turn, be tested as explained above. When the Forgejo runner modified to include the changes in the `wip-act-change` branch pass the end to end test of the `setup-forgejo` action, it is ready to be released.
+
+ACT can be released by merging the `wip-act-change` branch and by pushing a new tag, for instance `v48.8.20`. Once published, the Forgejo runner can be updated to default to this latest version knowing it already passed end to end tests with something like:
+
+```
+replace github.com/nektos/act => code.forgejo.org/forgejo/act v48.8.20
+```
+
+# Local debug
+
+The repositories are checked out in the same directory:
+
+- **runner**: [Forgejo runner](https://codeberg.org/forgejo/runner)
+- **act**: [ACT](https://codeberg.org/forgejo/act)
+- **setup-forgejo**: [setup-forgejo](https://codeberg.org/actions/setup-forgejo)
+
+## Install dependencies
+
+The dependencies are installed manually or with:
+
+```shell
+setup-forgejo/forgejo-dependencies.sh
+```
+
+## Build the Forgejo runner with the local ACT
+
+The Forgejo runner is rebuilt with the ACT directory by changing the `runner/go.mod` file to:
+
+```
+replace github.com/nektos/act => ../act
+```
+
+Running:
+
+```
+cd runner ; go mod tidy
+```
+
+Building:
+
+```shell
+cd runner ; rm -f forgejo-runner ; make forgejo-runner
+```
+
+## Run Forgejo and the runner
+
+A Forgejo instance is launched with:
+
+```shell
+cd setup-forgejo ; ./forgejo.sh setup
+firefox http://$(cat forgejo-ip):3000
+```
+
+The user is `root` with password `admin1234`. The runner is registered with:
+
+```
+cd setup-forgejo ; ./runner/forgejo-runner register --no-interactive --instance "http://$(cat forgejo-ip):3000/" --name runner --token $(cat forgejo-runner-token) --labels ubuntu-latest:docker://node:16-buster,self-hosted
+```
+
+And launched in debug mode with:
+
+```shell
+cd setup-forgejo ; ACTIONS_STEP_DEBUG=true ../runner/forgejo-runner daemon
+```

developer/index.md

@@ -7,3 +7,4 @@ This area will be targeted to people who want to hack Forgejo and adjust it to
 their needs.
 
 - [code.forgejo.org](code-forgejo-org)
+- [Forgejo runner implementation notes](forgejo-runner)