Add git to prepare performance testing (#332)

Author: maxday

Dockerfile

@@ -2,6 +2,10 @@ ARG image
 FROM $image
 ARG image
 
+# Install git so we can specify a specific git ref (ie: refs/head/my-feature) in package.json 
+# to install a specific dd-trace version for performance test
+RUN apk add git
+
 # Create the directory structure required for AWS Lambda Layer
 RUN mkdir -p /nodejs/node_modules/