feat(docker): add cache for faster rebuild (#1507)

- Closes #1502

docker/build/Dockerfile

@@ -8,10 +8,10 @@ ADD conf/config.cmake.dist /azerothcore/conf/config.cmake.dist
 ADD src /azerothcore/src
 ADD CMakeLists.txt /azerothcore/CMakeLists.txt
 
-RUN cd azerothcore; \
-    mkdir build; \
-    cd build; \
-    cmake ../ -DCMAKE_INSTALL_PREFIX=/azeroth-server -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -DTOOLS=0 -DSCRIPTS=1; \
-    MTHREADS=`grep -c ^processor /proc/cpuinfo`; MTHREADS=$(($MTHREADS + 2)); \
-    make -j $MTHREADS; \
-    make install -j $MTHREADS;
+ENTRYPOINT  cd azerothcore/build && \
+            cmake ../ -DCMAKE_INSTALL_PREFIX=/azeroth-server -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -DTOOLS=0 -DSCRIPTS=1 && \
+            MTHREADS=`grep -c ^processor /proc/cpuinfo`; MTHREADS=$(($MTHREADS + 2)) && \
+            make -j $MTHREADS && \
+            make install -j $MTHREADS && \
+            cp /azeroth-server/bin/worldserver /binworldserver && \
+            cp /azeroth-server/bin/authserver /binauthserver

docker/build/README.md

@@ -1,15 +1,35 @@
 # AzerothCore Dockerized Build
 
-The AzerothCore Build Dockerfile is not meant to create containers, it is a stage that both the [authserver](https://github.com/azerothcore/azerothcore-wotlk/tree/master/docker/authserver) and the [worldserver](https://github.com/azerothcore/azerothcore-wotlk/tree/master/docker/worldserver) docker images will use.
+The AzerothCore Build Dockerfile will create a container that will run the AC build.
 
-Note: every time you update your AzerothCore sources, you **must** build again this image and the authserver & worldserver images to get the new version on your docker containers.
+When this container runs, it will compile AC and generate:
 
-*For more information about Docker multi-stage builds, refer to the [docker multi-stage builds doc](https://docs.docker.com/develop/develop-images/multistage-build/).*
+- the build cache in the `docker/build/cache` directory
+- the `worldserver` executable file in `docker/worldserver/bin`
+- the `authserver` executable file in `docker/authserver/bin`
 
-# Usage
+The executable files will be used by the [authserver](https://github.com/azerothcore/azerothcore-wotlk/tree/master/docker/authserver) and the [worldserver](https://github.com/azerothcore/azerothcore-wotlk/tree/master/docker/worldserver) docker containers.
 
-To build the container image you have to be in the **main** folder of your local AzerothCore sources directory.
+Note: every time you update your AzerothCore sources, you **must** run again the build container and restart your `worldserver` and `authserver` containers.
+
+## Usage
+
+To build the container image you have to be in the **main** folder of your local AzerothCore sources directory and run:
 
 ```
-docker build -t azerothcore/build -f docker/build/Dockerfile .
+docker build -t acbuild -f docker/build/Dockerfile .
 ```
+
+Then you can launch the container to rebuild AC using:
+
+```
+docker run \
+    -v /$(pwd)/docker/build/cache:/azerothcore/build \
+    -v /$(pwd)/docker/worldserver/bin:/binworldserver \
+    -v /$(pwd)/docker/authserver/bin:/binauthserver \
+    acbuild
+```
+
+### Clearing the cache
+
+To clear the build cache, delete all files contained under the `docker/build/cache` directory.