Enables C# mode command line diff
Enables C# mode command line diff

When diffing on the command line, enabling this ensures that hunk headers will
use the containing construct (i.e. method, type, or namespace).

For example, instead of this (pay attention to the @@ line):

    diff --git a/src/netstandard/ref/System.Security.Cryptography.cs b/src/netstandard/ref/System.Security.Cryptography.cs
    index 9f68653..19d239a 100644
    --- a/src/netstandard/ref/System.Security.Cryptography.cs
    +++ b/src/netstandard/ref/System.Security.Cryptography.cs
    @@ -101,8 +101,20 @@ namespace System.Security.Cryptography
             public virtual byte[] ExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters) { throw null; }
             public virtual byte[] ExportPkcs8PrivateKey() { throw null; }
    +        public virtual byte[] ExportSubjectPublicKeyInfo() { throw null; }
             public virtual void FromXmlString(string xmlString) { }
         }
         public abstract partial class AsymmetricKeyExchangeDeformatter
         {

You'll see this:

    diff --git a/src/netstandard/ref/System.Security.Cryptography.cs b/src/netstandard/ref/System.Security.Cryptography.cs
    index 9f68653..19d239a 100644
    --- a/src/netstandard/ref/System.Security.Cryptography.cs
    +++ b/src/netstandard/ref/System.Security.Cryptography.cs
    @@ -101,8 +101,20 @@ public abstract partial class AsymmetricAlgorithm : System.IDisposable
             public virtual byte[] ExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters) { throw null; }
             public virtual byte[] ExportPkcs8PrivateKey() { throw null; }
    +        public virtual byte[] ExportSubjectPublicKeyInfo() { throw null; }
             public virtual void FromXmlString(string xmlString) { }
         }
         public abstract partial class AsymmetricKeyExchangeDeformatter
         {

ericstj/standard,ericstj/standard