fix: handle properties of complex Metadata types

`force-dev-tool changeset create` now handles properties of complex Metadata types.

Complex Metadata types can contain other Metadata types (e.g. a `CustomObject` can contain a `CustomField`) - changing **independent** children was already handled by `force-dev-tool changeset create` by creating a deployment with only the `CustomField` instead of the whole `CustomObject`.

However complex Metadata types can also have properties (e.g. a `CustomObject` has a `description`) and changing these properties was currently not handled.
When changing the `description` of a `CustomObject` force-dev-tool now creates a deployment with the `CustomObject` but only containing the properties without the named/independent child Metadata components.

The following exemplary changes should now be picked up correctly:

- changing the `description` of a CustomObject/Profile
- changing the `searchLayouts` of a CustomObject

This PR introduces a brand new suite for functional testing of `force-dev-tool changeset create` and is based on simulating a Git history with typical changes to Metadata.
See `test-functional/README.md` to get started.

This closes #13, closes #90, closes #137.

.gitignore

@@ -4,3 +4,5 @@ doc
 coverage
 npm-debug.log
 .vagrant
+.orgs.json
+.sfdx

.vscode/launch.json

@@ -1,9 +1,9 @@
 {
-	// Use IntelliSense to learn about possible attributes.
-	// Hover to view descriptions of existing attributes.
-	// For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
-	"version": "0.2.0",
-	"configurations": [{
+  // Use IntelliSense to learn about possible attributes.
+  // Hover to view descriptions of existing attributes.
+  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+  "version": "0.2.0",
+  "configurations": [{
 		"type": "node",
 		"request": "launch",
 		"name": "Mocha Tests",
@@ -18,5 +18,13 @@
 			"${workspaceFolder}/test",
 		],
 		"internalConsoleOptions": "openOnSessionStart"
-	}]
+	}, {
+      "type": "node",
+      "request": "attach",
+      "name": "Attach by Process ID",
+      "processId": "${command:PickProcess}",
+      "skipFiles": [
+        "<node_internals>/**"
+      ]
+  }]
 }

lib/metadata-file-container.js

@@ -87,6 +87,19 @@ MetadataFileContainer.prototype.diff = function(other) {
 					type: deletedComponent.type
 				}));
 			});
+			if (self.getMetadataType().childXmlNames) {
+				var selfContents = self.contentsWithoutChilds();
+				var otherContents = other.contentsWithoutChilds();
+				if (selfContents !== otherContents) {
+					other.updateContents(added, modified);
+					var component = other.getComponent();
+					modified.add(new MetadataComponent({
+						fullName: component.fullName,
+						fileName: filename,
+						type: component.type
+					}))
+				}
+			}
 		}
 
 	}
@@ -172,10 +185,56 @@ MetadataFileContainer.prototype.getGroupedAndSortedComponents = function() {
 	return map;
 };
 
+MetadataFileContainer.prototype.contentsWithoutChilds = function(includedChildComponents) {
+	var ret = this.contents.toString();
+
+	var childComponents = this.getMetadataType().childXmlNames;
+	if (childComponents) {
+		var parsed = new xmldoc.XmlDocument(this.contents);
+		var parentMetadata = '<' + parsed.name + ' xmlns="http://soap.sforce.com/2006/04/metadata">';
+		var tagIncludedChildNames = includedChildComponents ?
+			includedChildComponents.map(function(child) { return describeMetadataService.getType(child).tagName; }) : [];
+		var tagChildNames = childComponents.map(function(child) { return describeMetadataService.getType(child).tagName; })
+			.filter(function(child) { return !tagIncludedChildNames.includes(child); });
+		parsed.eachChild(function(child) {
+			var name = child.name;
+			if (!tagChildNames.includes(name)) {
+				parentMetadata += child.toString({
+					compressed: true,
+					trimmed: true,
+					preserveWhitespace: false
+				});
+			}
+		})
+		parentMetadata += '</' + parsed.name + '>';
+		//sax has an isssue with '&': https://github.com/isaacs/sax-js/issues/167
+		var document = new xmldoc.XmlDocument(parentMetadata.replace(new RegExp('&',"gm"), '&amp;'));
+		var indent4Spaces = function(str) {
+			return str.replace(/^(\s+)</gm, "$1$1<");
+		}
+		ret = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
+			indent4Spaces(document.toString({
+				compressed: false,
+				trimmed: false,
+				preserveWhitespace: !this.opts.ignoreWhitespace
+		}) + '\n');
+	}
+	return ret;
+}
+
 MetadataFileContainer.prototype.writeContents = function() {
 	var self = this;
 	self.contents = Buffer.from(self.toString());
 	return self;
+}
+
+MetadataFileContainer.prototype.updateContents = function(added, modified) {
+	var self = this;
+	var includedChildComponents = modified.manifestJSON.map(function(m) { return m.type; })
+			.concat(added.manifestJSON.map(function(m) { return m.type; })).filter(function(m) { return m !== undefined; });
+	var content = self.contentsWithoutChilds(includedChildComponents);
+	self.contents = Buffer.from(content.toString());
+	return self;
 };
 
 MetadataFileContainer.prototype.toString = function() {