Add support for jenkins agent jar file location in environment variables

README_inbound-agent.md

@@ -61,6 +61,7 @@ Optional environment variables:
 
 * `JENKINS_JAVA_BIN`: Path to Java executable to use instead of the default in PATH or obtained from JAVA_HOME
 * `JENKINS_JAVA_OPTS` : Java Options to use for the remoting process, otherwise obtained from JAVA_OPTS, **Warning** :exclamation: For more information on Windows usage, please see the **Windows Jenkins Java Opts** [section below](#windows-jenkins-java-opts).
+* `JENKINS_AGENT_FILE` : Jenkins agent jar file location, `/usr/share/jenkins/agent.jar` will be used if this is not set
 * `JENKINS_URL`: url for the Jenkins server, can be used as a replacement to `-url` option, or to set alternate jenkins URL
 * `JENKINS_TUNNEL`: (`HOST:PORT`) connect to this agent host and port instead of Jenkins server, assuming this one do route TCP traffic to Jenkins controller. Useful when when Jenkins runs behind a load balancer, reverse proxy, etc.
 * `JENKINS_SECRET`: (use only if not set as an argument) the secret as shown on the controller after creating the agent

jenkins-agent

@@ -26,6 +26,7 @@
 # Optional environment variables :
 # * JENKINS_JAVA_BIN : Java executable to use instead of the default in PATH or obtained from JAVA_HOME
 # * JENKINS_JAVA_OPTS : Java Options to use for the remoting process, otherwise obtained from JAVA_OPTS
+# * JENKINS_AGENT_FILE : Jenkins agent jar file location, /usr/share/jenkins/agent.jar will be used if this is not set
 # * REMOTING_OPTS : Generic way to pass additional CLI options to agent.jar (see -help)
 #
 # Deprecated environment variables (prefer setting REMOTING_OPTS)
@@ -109,6 +110,12 @@ else
 		fi
 	fi
 
+	if [ "$JENKINS_AGENT_FILE" ]; then
+		AGENT_FILE="$JENKINS_AGENT_FILE"
+	else
+		AGENT_FILE="/usr/share/jenkins/agent.jar"
+	fi
+
 	# if both required options are defined, do not pass the parameters
 	if [ -n "$JENKINS_SECRET" ]; then
 		case "$@" in
@@ -129,6 +136,6 @@ else
 	#TODO: Handle the case when the command-line and Environment variable contain different values.
 	#It is fine it blows up for now since it should lead to an error anyway.
 
-        exec $JAVA_BIN $JAVA_OPTIONS -jar /usr/share/jenkins/agent.jar $SECRET $AGENT_NAME $TUNNEL $URL $WORKDIR $WEB_SOCKET $DIRECT $PROTOCOLS $INSTANCE_IDENTITY $REMOTING_OPTS "$@"
+        exec $JAVA_BIN $JAVA_OPTIONS -jar $AGENT_FILE $SECRET $AGENT_NAME $TUNNEL $URL $WORKDIR $WEB_SOCKET $DIRECT $PROTOCOLS $INSTANCE_IDENTITY $REMOTING_OPTS "$@"
 
 fi