Merge pull request jenkinsci#54 from oleg-nenashev/workdir-env-var

 Add JENKINS_AGENT_WORKDIR env var (update of jenkinsci#44)

jenkins-slave

@@ -28,6 +28,7 @@
 # * JENKINS_URL : alternate jenkins URL
 # * JENKINS_SECRET : agent secret, if not set as an argument
 # * JENKINS_AGENT_NAME : agent name, if not set as an argument
+# * JENKINS_AGENT_WORKDIR : agent work directory, if not set by optional parameter -workDir
 
 if [ $# -eq 1 ]; then
 
@@ -45,6 +46,15 @@ else
 		fi ;;
 	esac
 
+	# if -workDir is not provided try env vars
+	if [ ! -z "$JENKINS_AGENT_WORKDIR" ]; then
+		case "$@" in
+			*"-workDir"*) echo "Warning: Work directory is defined twice in command-line arguments and the environment variable" ;;
+			*)
+			WORKDIR="-workDir $JENKINS_AGENT_WORKDIR" ;;
+		esac
+	fi
+
 	if [ -n "$JENKINS_URL" ]; then
 		URL="-url $JENKINS_URL"
 	fi
@@ -80,5 +90,5 @@ 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 $JAVA_OPTS $JNLP_PROTOCOL_OPTS -cp /usr/share/jenkins/slave.jar hudson.remoting.jnlp.Main -headless $TUNNEL $URL $OPT_JENKINS_SECRET $OPT_JENKINS_AGENT_NAME "$@"
+	exec java $JAVA_OPTS $JNLP_PROTOCOL_OPTS -cp /usr/share/jenkins/slave.jar hudson.remoting.jnlp.Main -headless $TUNNEL $URL $WORKDIR $OPT_JENKINS_SECRET $OPT_JENKINS_AGENT_NAME "$@"
 fi