Allow JVM options to be set via environment variable

Thanks go to Jacek Kowalski (jacekkow@0b247732408f877aabca3adf77381fc37776f43a)

Author: flaix

README.md

@@ -7,6 +7,9 @@ These instructions assume you are running Linux and you have already [installed
 
 You can use the official [Gitblit Docker image](https://hub.docker.com/r/gitblit/gitblit).
 
+See the [Docker Hub Readme](hub-readme.md) for more detailed usage information.
+
+
 ### Start a Gitblit instance
 
 

docker-entrypoint.sh

@@ -1,8 +1,15 @@
 #!/bin/sh
 set -e
 
+
+# allow JVM options to be set from outside
+if [ -z "$JAVA_OPTS" ] ; then
+	JAVA_OPTS="-Xmx1024M"
+fi
+
+
 gitblit_path=/opt/gitblit
-gitblit="java -server -Xmx1024M -Djava.awt.headless=true -cp ${gitblit_path}/gitblit.jar:${gitblit_path}/ext/* com.gitblit.GitBlitServer"
+gitblit="java -server $JAVA_OPTS -Djava.awt.headless=true -cp ${gitblit_path}/gitblit.jar:${gitblit_path}/ext/* com.gitblit.GitBlitServer"
 
 
 # use gosu or su-exec to step down from root

hub-readme.md

@@ -91,6 +91,17 @@ gitblit-config  /var/lib/docker/volumes/gitblit-config/_data   local
 gitblit-repos   /var/lib/docker/volumes/gitblit-repos/_data    local
 ```
 
+It also makes updates easier. Simply provide the same named volumes to the new version of the container:
+
+```console
+$ sudo docker pull gitblit/gitblit:rpc
+$ sudo docker stop gitblit
+$ sudo docker container rm gitblit
+$ sudo docker run -d --name gitblit -v gitblit-data:/var/opt/gitblit -p 8443:8443 -p 29418:29418 gitblit/gitblit:rpc
+```
+
+Updating with anonymous volumes (you didn't provide a name for) requires you to either find out the volume id from the current running container and reusing that id for the new container, or to use the `--volumes-from` parameter, which requires the old container to still be around.
+
 
 ### Temporary webapp data
 
@@ -105,6 +116,19 @@ $ sudo docker run -d --name gitblit --tmpfs /var/opt/gitblit/temp -p 8443:8443 g
 ```
 
 
+## Configuration
+
+Configure the gitblit instance by adding your custom settings to the file `gitblit.properties` in the directory `/var/opt/gitbit/etc` in the container.
+
+### JVM options
+
+The gitblit server starts by default with the JVM option `-Xmx1024M`. You can override this by providing the `JAVA_OPTS` environment variable.
+
+```console
+$ sudo docker run -d --name gitblit -e "JAVA_OPTS=-Xmx2048m"  -p 8443:8443 gitblit/gitblit:rpc
+```
+
+
 ## User and group id
 
 Since image version 1.9.0-3 the gitblit process will be started as a non privileged user. The user id and group id used by the images are both `8117`.