removed ENV WORKDIR layers, reorg the commands in groups with comments

and black lines when possible. Removed redundant mkdir command

Dockerfile

@@ -1,25 +1,26 @@
 FROM alpine:3.7
-WORKDIR /usr/src/paperless
-COPY requirements.txt /usr/src/paperless/
+
 # Copy application
+COPY requirements.txt /usr/src/paperless/
 COPY src/ /usr/src/paperless/src/
 COPY data/ /usr/src/paperless/data/
 COPY media/ /usr/src/paperless/media/
-# Set export directory
-ENV PAPERLESS_EXPORT_DIR /export
-# Set consumption directory
-ENV PAPERLESS_CONSUMPTION_DIR /consume
 COPY scripts/docker-entrypoint.sh /sbin/docker-entrypoint.sh
+
+# Set export and consumption directories
+ENV PAPERLESS_EXPORT_DIR=/export \
+    PAPERLESS_CONSUMPTION_DIR=/consume
+
 # Install dependencies
 RUN apk --no-cache --update add \
         python3 gnupg libmagic bash \
         sudo tesseract-ocr imagemagick ghostscript unpaper && \
     apk --no-cache add --virtual .build-dependencies \
         python3-dev gcc musl-dev zlib-dev jpeg-dev && \
-## Install python dependencies
+# Install python dependencies
     python3 -m ensurepip && \
     rm -r /usr/lib/python*/ensurepip && \
-    mkdir -p /usr/src/paperless && \
+    cd /usr/src/paperless && \
     pip3 install --no-cache-dir -r requirements.txt && \
 # Remove build dependencies
     apk del .build-dependencies && \
@@ -34,8 +35,9 @@ RUN apk --no-cache --update add \
     mkdir -p $PAPERLESS_EXPORT_DIR && \
 # Setup entrypoint
     chmod 755 /sbin/docker-entrypoint.sh
+
 WORKDIR /usr/src/paperless/src
-# Mount volumes
+# Mount volumes and set Entrypoint
 VOLUME ["/usr/src/paperless/data", "/usr/src/paperless/media", "/consume", "/export"]
 ENTRYPOINT ["/sbin/docker-entrypoint.sh"]
 CMD ["--help"]