document how to use build_runner for a short debug loop

.forgejo/workflows/integration.yml

@@ -8,6 +8,14 @@ jobs:
           set -x
           LXC_IP_PREFIX=10.0.9 ./forgejo-dependencies.sh
           ./forgejo.sh setup root admin1234 codeberg.org/forgejo/forgejo:1.19
+          #
+          # 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 http://code.forgejo.org/forgejo/runner branch-under-debug
+          # export PATH=$(pwd)/forgejo-runner:$PATH
+          #
           ./forgejo-runner.sh setup
           export FORGEJO_RUNNER_LOGS=forgejo-runner.log
           ./forgejo-test-helper.sh run_workflow testdata/demo http://root:admin1234@$(cat forgejo-ip):3000 root demo setup-forgejo $(cat forgejo-token) > /tmp/output

action.yml

@@ -21,6 +21,11 @@ description: |
     Create the repository `$forgejo/root/testrepo` and populate it with the
     content of the `testrepo` directory. The SHA of the tip of the repository
     is in the output, starting with `sha=`.
+  * `forgejo-test-helper.sh build_runner $forgejo/forgejo/runner v1.4.1`
+    Builds the forgejo runner from source in `./forgejo-runner/forgejo-runner`.
+    `export PATH=$(pwd)/forgejo-runner:$PATH` will ensure that calling `forgejo-runner.sh`
+    will use this binary instead of downloading a released version of the runner.
+    If the version is not specified, build from the main branch.
 
   The combination of `push_self_action` and `run_workflow` allows to
   run Forgejo Actions workflows from `testrepo` that use the action

forgejo-test-helper.sh

@@ -21,22 +21,23 @@ function dependency_go() {
 
 function checkout() {
     local git="$1"
-    if ! test -d forgejo-runner ; then
+    rm -fr forgejo-runner
     git clone $git forgejo-runner
-    fi
 }
 
-function build() {
+function build_runner() {
     local git="$1"
-    local version="$2"
+    local version="${2:-main}"
 
     (
 	checkout "$git"
+	dependency_go
 	cd forgejo-runner
 	git checkout "$version"
 	make build
-	export PATH=$PATH:$(pwd)
     )
+    export PATH=$PATH:$(pwd)/forgejo-runner
+    forgejo-runner --version
 }
 
 function api() {