Configure from installation copies

When starting several runners, the same token will be returned. In order
to be able to run several runners, they need to be configured from
different working directories, and these directories need to contain an
entire copy of the runner installation.

Arrange for two sub-directories to be created in the working directory:
one called `runner` will contain the copy of the installation tree,
another called `work` will be where the runner will be "working", e.g.
checkout repositories, etc.

runner/runner.sh

@@ -146,7 +146,25 @@ fi
 KRUNVM_RUNNER_BIN=$(basename "$0")
 KRUNVM_RUNNER_BIN="${KRUNVM_RUNNER_BIN%.sh}-$RUNNER_ID"
 
-configure() {
+# Install a copy of the runner installation into the work directory. Perform a
+# minimal verification of the installation through checking that there is a
+# config.sh script executable within the copy.
+runner_install() {
+  # Make a directory where to install a copy of the runner.
+  if ! [ -d "${RUNNER_WORKDIR%/}/runner" ]; then
+    mkdir -p "${RUNNER_WORKDIR%/}/runner"
+    verbose "Created runner directory ${RUNNER_WORKDIR%/}/runner"
+  fi
+  verbose "Installing runner in ${RUNNER_WORKDIR%/}/runner"
+  # shellcheck disable=SC2086 # We want to expand here
+  cp -af ${RUNNER_INSTALL%/}/* "${RUNNER_WORKDIR%/}/runner/"
+  check_command "${RUNNER_WORKDIR%/}/runner/config.sh"
+}
+
+
+# Configure the runner and register it at GitHub. This will use the runner
+# installation copy from runner_install.
+runner_configure() {
   verbose "Registering $RUNNER_SCOPE runner '$RUNNER_NAME' for $RUNNER_URL"
   if [ -n "${RUNNER_PAT:-}" ]; then
     if [ -n "${RUNNER_TOKEN:-}" ]; then
@@ -162,15 +180,24 @@ configure() {
                       -T "$RUNNER_PAT" )
   fi
 
+  # Bail out if no token is available
   if [ -z "${RUNNER_TOKEN:-}" ]; then
     error "No runner token provided or acquired"
   fi
 
+  # Create the work directory. This is where the runner will be working, e.g.
+  # checking out repositories, actions, etc.
+  if ! [ -d "${RUNNER_WORKDIR%/}/work" ]; then
+    mkdir -p "${RUNNER_WORKDIR%/}/work"
+    verbose "Created work directory ${RUNNER_WORKDIR%/}/work"
+  fi
+
+  # Construct CLI arguments for the runner configuration
   set -- \
     --url "$RUNNER_URL" \
     --token "$RUNNER_TOKEN" \
     --name "$RUNNER_NAME" \
-    --work "$RUNNER_WORKDIR" \
+    --work "${RUNNER_WORKDIR%/}/work" \
     --labels "$RUNNER_LABELS" \
     --runnergroup "$RUNNER_GROUP" \
     --unattended \
@@ -182,18 +209,14 @@ configure() {
     set -- "$@" --disableupdate
   fi
 
+  # Configure the runner from the installation copy
   verbose "Configuring runner ${RUNNER_NAME}..."
-  debug "Configuration details: $*"
-  RUNNER_ALLOW_RUNASROOT=1 "$RUNNER_INSTALL/config.sh" "$@"
-
-  if ! [ -d "$RUNNER_WORKDIR" ]; then
-    mkdir -p "$RUNNER_WORKDIR"
-    verbose "Created work directory $RUNNER_WORKDIR"
-  fi
+  runner_control config.sh "$@"
 }
 
 
-unregister() {
+# Unregister the runner from GitHub. This will use the runner installation copy
+runner_unregister() {
   verbose "Caught termination signal, unregistering runner"
   if [ -n "${RUNNER_PAT:-}" ]; then
     verbose "Requesting (back) runner token with PAT"
@@ -206,7 +229,20 @@ unregister() {
                       -T "$RUNNER_PAT" )
   fi
   verbose "Removing runner at GitHub"
-  RUNNER_ALLOW_RUNASROOT=1 "$RUNNER_INSTALL/config.sh" remove --token "$RUNNER_TOKEN"
+  runner_control config.sh remove --token "$RUNNER_TOKEN"
+}
+
+
+# Run one of the runner scripts from the installation copy. The implementation
+# temporary changes directory before calling the script.
+runner_control() {
+  cwd=$(pwd)
+  cd "${RUNNER_WORKDIR%/}/runner"
+  script=./${1}; shift
+  check_command "$script"
+  debug "Running $script $*"
+  RUNNER_ALLOW_RUNASROOT=1 "$script" "$@"
+  cd "$cwd"
 }
 
 
@@ -255,11 +291,6 @@ if [ -z "$RUNNER_PRINCIPAL" ]; then
   error "Principal must be set to name of repo, org or enterprise"
 fi
 
-if [ "$#" = 0 ]; then
-  warn "No command to run, will take defaults"
-  set -- /opt/actions-runner/bin/Runner.Listener run --startuptype service
-fi
-
 # Setup variables that would have been missing. These depends on the main
 # variables, so we do it here rather than at the top of the script.
 debug "Setting up missing defaults"
@@ -296,11 +327,17 @@ case "$RUNNER_SCOPE" in
     ;;
 esac
 
-# Configure the runner
-configure
+# Install runner binaries into SEPARATE directory, then configure from there
+runner_install
+runner_configure
+
+if [ "$#" = 0 ]; then
+  warn "No command to run, will take defaults"
+  set -- "${RUNNER_WORKDIR%/}/runner/bin/Runner.Listener" run --startuptype service
+fi
 
 # Capture termination signals
-trap unregister INT TERM QUIT
+trap runner_unregister INT TERM QUIT
 
 # Start the docker daemon. Prefer podman if available (it will be the only one
 # available, unless the dockerd is installed in the future)