add blocks support

data/projects/project1/config.yaml

@@ -21,6 +21,13 @@ trigger:
         - status: done
           project: project2
 
+blockedBy:
+    # - project2
+    - !!js/regexp /project2|nci/
+
+blocks:
+    - project2
+
 steps:
     - cmd: >
         echo "long multiline string" &&

lib/node.js

@@ -12,6 +12,19 @@ function Node(params) {
 
 exports.Node = Node;
 
+Node.prototype._getBlockerExecutor = function(getBlockers, getTarget) {
+	return _(this.executors).find(function(executor) {
+		var target = getTarget(executor);
+		return _(getBlockers(executor)).find(function(blocker) {
+			if (_(blocker).isRegExp()) {
+				return blocker.test(target);
+			} else {
+				return blocker === target;
+			}
+		});
+	})
+};
+
 Node.prototype.getExecutorWaitReason = function(project) {
 	var waitReason;
 
@@ -19,6 +32,37 @@ Node.prototype.getExecutorWaitReason = function(project) {
 		waitReason = 'All executors are busy';
 	} else if (project.name in this.executors) {
 		waitReason = 'Project already running on node';
+	} else {
+		var blockerExecutor;
+
+		if (project.blockedBy) {
+			blockerExecutor = this._getBlockerExecutor(
+				function(executor) {
+					return project.blockedBy;
+				},
+				function(executor) {
+					return executor.project.name;
+				}
+			);
+		}
+
+		if (!blockerExecutor) {
+			blockerExecutor = this._getBlockerExecutor(
+				function(executor) {
+					return executor.project.blocks;
+				},
+				function(executor) {
+					return project.name;
+				}
+			);
+		}
+
+		if (blockerExecutor) {
+			waitReason = (
+				'Blocked by currently running "' +
+				blockerExecutor.project.name + '"'
+			);
+		}
 	}
 
 	return waitReason;