Fix to test the new milestone offset

Dockerfile

@@ -5,6 +5,8 @@ FROM --platform=linux/amd64 heroku/heroku:${STACK_VERSION}-build as build
 ARG STACK_VERSION
 ENV STACK="heroku-${STACK_VERSION}"
 
+ARG GOOGLE_CHROME_MILESTONE_OFFSET
+
 # On Heroku-24 and later the default user is not root.
 # Once support for Heroku-22 and older is removed, the `useradd` steps below can be removed.
 USER root
@@ -15,6 +17,9 @@ USER non-root-user
 RUN mkdir -p /tmp/build /tmp/cache /tmp/env
 COPY --chown=non-root-user . /buildpack
 
+# Emulate the platform providing app config vars via env directory
+RUN if [ -n "${GOOGLE_CHROME_MILESTONE_OFFSET}" ]; then echo "${GOOGLE_CHROME_MILESTONE_OFFSET}" > /tmp/env/GOOGLE_CHROME_MILESTONE_OFFSET; fi
+
 # Sanitize the environment seen by the buildpack, to prevent reliance on
 # environment variables that won't be present when it's run by Heroku CI.
 RUN env -i PATH=$PATH HOME=$HOME STACK=$STACK /buildpack/bin/detect /tmp/build

bin/compile

@@ -65,8 +65,9 @@ if [ -f "$ENV_DIR/GOOGLE_CHROME_MILESTONE_OFFSET" ]; then
   fi
 
   latest_version_per_milestone="$(curl --silent --show-error --fail --retry 3 --retry-connrefused --connect-timeout 10 "https://googlechromelabs.github.io/chrome-for-testing/latest-versions-per-milestone.json")"
-  VERSION="$(echo $latest_version_per_milestone | jq --arg milestone_offset="$milestone_offset" value '.milestones | map(.) | sort_by(.milestone)[($milestone_offset | tonumber)] | .version')"
+  VERSION="$(echo $latest_version_per_milestone | jq --raw-output --arg milestone_offset "$milestone_offset" '.milestones | map(.) | sort_by(.milestone)[($milestone_offset | tonumber)] | .version')"
   echo "Resolved milestone offset $milestone_offset to version $VERSION" | indent
+  INSTALLED_DESCRIPTION="milestone offset $milestone_offset"
 
 else
   # Detect requested channel or default to stable
@@ -80,6 +81,7 @@ else
   CHANNEL="$(echo -n "$channel" | awk '{ print toupper($0) }')"
   VERSION="$(curl --silent --show-error --fail --retry 3 --retry-connrefused --connect-timeout 10 "https://googlechromelabs.github.io/chrome-for-testing/LATEST_RELEASE_$CHANNEL")"
   echo "Resolved $CHANNEL version $VERSION" | indent
+  INSTALLED_DESCRIPTION="$CHANNEL"
 fi
 
 echo "Downloading Chrome" | indent
@@ -107,4 +109,4 @@ export PATH="$BUILD_DIR/.chrome-for-testing/chrome-linux64:$BUILD_DIR/.chrome-fo
 which chrome | indent
 which chromedriver | indent
 
-echo "Installed Chrome for Testing $CHANNEL version $VERSION" | indent
+echo "Installed Chrome for Testing $INSTALLED_DESCRIPTION version $VERSION" | indent