Aegisub/build/tasks.props

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="12.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <_PropertySheetDisplayName>Custom Tasks</_PropertySheetDisplayName>
  </PropertyGroup>

  <UsingTask TaskName="GitVersion" AssemblyFile="$(AegisubBinaryDir)BuildTasks.dll" />

  <UsingTask TaskName="CalculateOutputDir" TaskFactory="CodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll" >
    <ParameterGroup>
      <Items ParameterType="Microsoft.Build.Framework.ITaskItem[]" Required="true" />
      <SourceDir Required="true" />
      <DestinationDir Required="true" />
      <Outputs ParameterType="Microsoft.Build.Framework.ITaskItem[]" Output="true" />
    </ParameterGroup>
    <Task>
      <Code Type="Fragment" Language="cs"><![CDATA[
        Outputs = new TaskItem[Items.Length];
        char[] backslash = new char[] {'\\'};
        var srcdir = SourceDir.Replace('/', '\\').TrimEnd(backslash) + "\\";
        var dstdir = DestinationDir.Replace('/', '\\').TrimEnd(backslash) + "\\";
        int i = 0;
        foreach (var item in Items) {
          var itemDir = item.GetMetadata("RelativeDir"); // the dir specified in the item Include= attribute
          var outputDir = itemDir.Replace(srcdir, dstdir).Replace('/', '\\').TrimEnd(backslash) + "\\";
          var output = new TaskItem(item);
          ((ITaskItem2)output).SetMetadataValueLiteral("OutputDir", outputDir);
          Outputs[i] = output;
          i++;
        }
      ]]></Code>
    </Task>
  </UsingTask>
</Project>