decrease docker rebuild time after source code change

Dockerfile

@@ -1,7 +1,7 @@
-#Base image
+# Base image
 FROM ubuntu:18.04
 
-#Labels and Credits
+# Labels and Credits
 LABEL \
     name="MobSF" \
     author="Ajin Abraham <[email protected]>" \
@@ -10,7 +10,7 @@ LABEL \
     contributor_2="Vincent Nadal <[email protected]>" \
     description="Mobile Security Framework (MobSF) is an automated, all-in-one mobile application (Android/iOS/Windows) pen-testing, malware analysis and security assessment framework capable of performing static and dynamic analysis."
 
-#Environment vars
+# Environment vars
 ENV DEBIAN_FRONTEND="noninteractive" \
     ANALYZER_IDENTIFIER="" \
     JDK_FILE="openjdk-12_linux-x64_bin.tar.gz" \
@@ -19,7 +19,7 @@ ENV DEBIAN_FRONTEND="noninteractive" \
 ENV JDK_URL="https://download.java.net/java/GA/jdk12/GPL/${JDK_FILE}" \
     WKH_URL="https://builds.wkhtmltopdf.org/0.12.1.4/${WKH_FILE}"
 
-#see https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#run
+# See https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#run
 RUN apt update -y && apt install -y \
     build-essential \
     git \
@@ -32,7 +32,7 @@ RUN apt update -y && apt install -y \
     fontconfig-config \
     libjpeg-turbo8 \
     libxrender1 \
-    libfontconfig1 \ 
+    libfontconfig1 \
     libxext6 \
     fontconfig \
     xfonts-75dpi \
@@ -42,47 +42,32 @@ RUN apt update -y && apt install -y \
     python3-pip \
     wget \
     android-tools-adb
-     
-#set locales
+
+# Set locales
 RUN locale-gen en_US.UTF-8
 ENV LANG='en_US.UTF-8' LANGUAGE='en_US:en' LC_ALL='en_US.UTF-8'
 
-#Install Wkhtmltopdf
+# Install Wkhtmltopdf
 RUN wget --quiet -O /tmp/${WKH_FILE} "${WKH_URL}" && \
     dpkg -i /tmp/${WKH_FILE} && \
     apt-get install -f -y --no-install-recommends && \
     ln -s /usr/local/bin/wkhtmltopdf /usr/bin && \
     rm -f /tmp/${WKH_FILE}
 
-#Install OpenJDK12
+# Install OpenJDK12
 RUN wget --quiet "${JDK_URL}" && \
     tar zxf "${JDK_FILE}" && \
     rm -f "${JDK_FILE}"
-ENV JAVA_HOME="/jdk-12" 
+ENV JAVA_HOME="/jdk-12"
 ENV PATH="$JAVA_HOME/bin:$PATH"
 
-#Add MobSF master
-COPY . /root/Mobile-Security-Framework-MobSF
 WORKDIR /root/Mobile-Security-Framework-MobSF
+COPY ./requirements.txt .
 
-#Enable Use Home Directory and set adb path
-RUN sed -i 's/USE_HOME = False/USE_HOME = True/g' MobSF/settings.py && \
-    sed -i "s#ADB_BINARY = ''#ADB_BINARY = '/usr/bin/adb'#" MobSF/settings.py
-
-#Postgres support is set to false by default
-ARG POSTGRES=False
-#check if Postgres support needs to be enabled 
-WORKDIR /root/Mobile-Security-Framework-MobSF/scripts
-RUN chmod +x postgres_support.sh; sync; ./postgres_support.sh $POSTGRES
-WORKDIR /root/Mobile-Security-Framework-MobSF
-
-#Add apktool working path
-RUN mkdir -p /root/.local/share/apktool/framework
-
-#Install Dependencies
+# Install Dependencies
 RUN pip3 install --quiet --no-cache-dir -r requirements.txt
 
-#Cleanup
+# Cleanup
 RUN \
     apt remove -y \
         git \
@@ -97,7 +82,24 @@ RUN \
     apt autoremove -y && \
     rm -rf /var/lib/apt/lists/* /tmp/* > /dev/null 2>&1
 
-#Expose MobSF Port
+# Copy source code
+COPY . .
+
+# Enable Use Home Directory and set adb path
+RUN sed -i 's/USE_HOME = False/USE_HOME = True/g' MobSF/settings.py && \
+    sed -i "s#ADB_BINARY = ''#ADB_BINARY = '/usr/bin/adb'#" MobSF/settings.py
+
+# Postgres support is set to false by default
+ARG POSTGRES=False
+# Check if Postgres support needs to be enabled
+WORKDIR /root/Mobile-Security-Framework-MobSF/scripts
+RUN chmod +x postgres_support.sh; sync; ./postgres_support.sh $POSTGRES
+WORKDIR /root/Mobile-Security-Framework-MobSF
+
+# Add apktool working path
+RUN mkdir -p /root/.local/share/apktool/framework
+
+# Expose MobSF Port
 EXPOSE 8000
 # MobSF Proxy
 EXPOSE 1337
@@ -106,5 +108,5 @@ RUN python3 manage.py makemigrations && \
     python3 manage.py makemigrations StaticAnalyzer && \
     python3 manage.py migrate
 
-#Run MobSF
+# Run MobSF
 CMD ["gunicorn", "-b", "0.0.0.0:8000", "MobSF.wsgi:application", "--workers=1", "--threads=10", "--timeout=1800"]