Add and export a ViewOptionDefinition for controlling visibility of t…

…he diff margin

BasicSccProvider.csproj

@@ -97,6 +97,7 @@
   <ItemGroup>
     <Compile Include="Diff\BackgroundParser.cs" />
     <Compile Include="Diff\DiffFormatNames.cs" />
+    <Compile Include="Diff\DiffMarginEnabled.cs" />
     <Compile Include="Diff\DiffParseResultEventArgs.cs" />
     <Compile Include="Diff\DiffRemovedEditorFormatDefinition.cs" />
     <Compile Include="Diff\DiffModificationEditorFormatDefinition.cs" />
@@ -105,6 +106,7 @@
     <Compile Include="Diff\DiffMarginFactory.cs" />
     <Compile Include="Diff\DiffUpdateBackgroundParser.cs" />
     <Compile Include="Diff\GitCommands.cs" />
+    <Compile Include="Diff\GitTextViewOptions.cs" />
     <Compile Include="Diff\HunkRange.cs" />
     <Compile Include="Diff\HunkRangeInfo.cs" />
     <Compile Include="Diff\IGitCommands.cs" />

Diff/DiffMarginEnabled.cs

@@ -0,0 +1,27 @@
+namespace GitScc.Diff
+{
+    using System.ComponentModel.Composition;
+    using Microsoft.VisualStudio.Text.Editor;
+    using Microsoft.VisualStudio.Utilities;
+
+    [Export(typeof(EditorOptionDefinition))]
+    [Name(GitTextViewOptions.DiffMarginName)]
+    public sealed class DiffMarginEnabled : ViewOptionDefinition<bool>
+    {
+        public override bool Default
+        {
+            get
+            {
+                return true;
+            }
+        }
+
+        public override EditorOptionKey<bool> Key
+        {
+            get
+            {
+                return GitTextViewOptions.DiffMarginId;
+            }
+        }
+    }
+}

Diff/GitTextViewOptions.cs

@@ -0,0 +1,11 @@
+namespace GitScc.Diff
+{
+    using Microsoft.VisualStudio.Text.Editor;
+
+    public static class GitTextViewOptions
+    {
+        public const string DiffMarginName = "GitScc/DiffMarginName";
+
+        public static readonly EditorOptionKey<bool> DiffMarginId = new EditorOptionKey<bool>(DiffMarginName);
+    }
+}