Automatically package Gem, will try and execute but continue if it fails (if Gem's not installed)

Author: Jake Ginnivan

GitVersionExe/GemAssets/gitversion.gemspec

@@ -2,7 +2,7 @@ Gem::Specification.new do |spec|
   spec.platform    = Gem::Platform::RUBY
   spec.name        = 'gitversion'
   spec.licenses    = ['MIT']
-  spec.version     = '0.20.0'
+  spec.version     = '$version$'
   spec.summary     = 'Derives SemVer information from a repository following GitFlow or GitHubFlow.'
   spec.description = <<-EOF
 Derives SemVer information from a repository following GitFlow or GitHubFlow.

GitVersionExe/GitVersionExe.csproj

@@ -98,6 +98,28 @@
     </ItemGroup>
     <Delete Files="@(ExeFilesToDelete)" />
   </Target>
+  <UsingTask TaskName="ReplaceFileText" TaskFactory="CodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll">
+    <ParameterGroup>
+      <InputFilename ParameterType="System.String" Required="true" />
+      <OutputFilename ParameterType="System.String" Required="true" />
+      <MatchExpression ParameterType="System.String" Required="true" />
+      <ReplacementText ParameterType="System.String" Required="true" />
+    </ParameterGroup>
+    <Task>
+      <Reference Include="System.Core" />
+      <Using Namespace="System" />
+      <Using Namespace="System.IO" />
+      <Using Namespace="System.Text.RegularExpressions" />
+      <Code Type="Fragment" Language="cs">
+        <![CDATA[
+            File.WriteAllText(
+                OutputFilename,
+                Regex.Replace(File.ReadAllText(InputFilename), MatchExpression, ReplacementText)
+                );
+          ]]>
+      </Code>
+    </Task>
+  </UsingTask>
   <Target Name="AfterBuild" DependsOnTargets="Clean">
     <!-- NugetExeBuild -->
     <MakeDir Directories="$(SolutionDir)NuGetExeBuild" />
@@ -122,6 +144,18 @@
       <GemFiles Include="$(ProjectDir)GemAssets\*.gemspec" />
     </ItemGroup>
     <Copy SourceFiles="@(GemFiles)" DestinationFiles="@(GemFiles->'$(SolutionDir)GemBuild\%(RecursiveDir)%(Filename)%(Extension)')" />
+    <Copy SourceFiles="$(ProjectDir)GemAssets\gitversion" DestinationFolder="$(SolutionDir)GemBuild\bin" />
+    <Copy SourceFiles="$(ProjectDir)GemAssets\gitversion.gemspec" DestinationFolder="$(SolutionDir)GemBuild" />
+
+    <ReplaceFileText
+        InputFilename="$(SolutionDir)GemBuild\gitversion.gemspec"
+        OutputFilename="$(SolutionDir)GemBuild\gitversion.gemspec"
+        MatchExpression="\$version\$"
+        ReplacementText="$(GitVersion_SemVer)"
+        Condition="'$(GitVersion_SemVer)' != ''"/>
+    
+    <Exec Command="gem build gitversion.gemspec" ContinueOnError="True"
+          WorkingDirectory="$(SolutionDir)GemBuild" Condition="'$(GitVersion_SemVer)' != ''" />
   </Target>
   <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
     <PropertyGroup>