Improve docker build times by 28%

From 53s to 38s on my machine (with --no-cache)

Author: iwishiwasaneagle

Dockerfile

@@ -1,17 +1,12 @@
-FROM python:3.7-slim-buster
+FROM python:3.7-slim
 
 RUN apt-get update
 RUN apt-get -y install git jq
 
-COPY entrypoint.sh /action/entrypoint.sh
-COPY run_action.py /action/run_action.py
-COPY duplicate_code_detection.py /action/duplicate_code_detection.py
-COPY requirements.txt /action/requirements.txt
+COPY duplicate_code_detection.py requirements.txt run_action.py entrypoint.sh /action/
 
-RUN pip3 install -r /action/requirements.txt
-RUN pip3 install requests
-RUN python3 -c "import nltk; nltk.download('punkt')"
-# nltk_data ends up in /root so python can't find it
-RUN ln -s /root/nltk_data /usr/local/nltk_data
+RUN pip3 install -r /action/requirements.txt requests && \
+    python3 -c "import nltk; nltk.download('punkt')" && \
+    ln -s /root/nltk_data /usr/local/nltk_data 
 
 ENTRYPOINT ["/action/entrypoint.sh"]