git diff hunk header for API contract files

[KalleOlaviNiemitalo]

git diff comparing versions of an API contract file normally shows the namespace in the hunk header. For example, comparing 2.0.0-beta4.23171.1 to 2.0.0-beta4.23172.1: git diff 02a776b901846b96cc2a7442b2032102944cafa9 0403596afba9f622468d26c15a81fa17e881b1df -- "src/System.CommandLine.ApiCompatibility.Tests/*.txt" (truncated for brevity):

diff --git a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
index e0da19de..14df6235 100644
--- a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
+++ b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
@@ -72,8 +72,6 @@ System.CommandLine
     public CommandLineBuilder UseExceptionHandler(System.Func<System.Exception,System.CommandLine.Invocation.InvocationContext,System.Int32> onException = null, System.Int32 errorExitCode = 1)
     public CommandLineBuilder UseHelp(System.Nullable<System.Int32> maxWidth = null)
     public CommandLineBuilder UseHelp(System.String name, System.String[] helpAliases)
-    public CommandLineBuilder UseHelp(System.Action<System.CommandLine.Help.HelpContext> customize, System.Nullable<System.Int32> maxWidth = null)
-    public CommandLineBuilder UseHelpBuilder(System.Func<System.CommandLine.Invocation.InvocationContext,System.CommandLine.Help.HelpBuilder> getHelpBuilder)
     public CommandLineBuilder UseParseDirective(System.Int32 errorExitCode = 1)
     public CommandLineBuilder UseParseErrorReporting(System.Int32 errorExitCode = 1)
     public CommandLineBuilder UseSuggestDirective()
@@ -83,7 +81,7 @@ System.CommandLine
     public CommandLineBuilder UseVersionOption(System.String name, System.String[] aliases)
   public class CommandLineConfiguration
     public static CommandLineBuilder CreateBuilder(Command rootCommand)
-    .ctor(Command command, System.Boolean enablePosixBundling = True, System.Boolean enableTokenReplacement = True, System.Func<System.CommandLine.Invocation.InvocationContext,System.CommandLine.Help.HelpBuilder> helpBuilderFactory = null, System.CommandLine.Parsing.TryReplaceToken tokenReplacer = null)
+    .ctor(Command command, System.Boolean enablePosixBundling = True, System.Boolean enableTokenReplacement = True, System.CommandLine.Parsing.TryReplaceToken tokenReplacer = null)
     public System.Collections.Generic.IReadOnlyList<Directive> Directives { get; }
     public System.Boolean EnablePosixBundling { get; }
     public System.Boolean EnableTokenReplacement { get; }

With a little configuration, I can make it show the name of the type instead.

• .git/info/attributes:

  /src/System.CommandLine.ApiCompatibility.Tests/*.txt diff=api-contract
  

• .git/config:

  [diff "api-contract"]
          xfuncname = "^ {,2}([^ ].*)$"

Then it shows this instead (truncated again):

diff --git a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
index e0da19de..14df6235 100644
--- a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
+++ b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
@@ -72,8 +72,6 @@ public class CommandLineBuilder
     public CommandLineBuilder UseExceptionHandler(System.Func<System.Exception,System.CommandLine.Invocation.InvocationContext,System.Int32> onException = null, System.Int32 errorExitCode = 1)
     public CommandLineBuilder UseHelp(System.Nullable<System.Int32> maxWidth = null)
     public CommandLineBuilder UseHelp(System.String name, System.String[] helpAliases)
-    public CommandLineBuilder UseHelp(System.Action<System.CommandLine.Help.HelpContext> customize, System.Nullable<System.Int32> maxWidth = null)
-    public CommandLineBuilder UseHelpBuilder(System.Func<System.CommandLine.Invocation.InvocationContext,System.CommandLine.Help.HelpBuilder> getHelpBuilder)
     public CommandLineBuilder UseParseDirective(System.Int32 errorExitCode = 1)
     public CommandLineBuilder UseParseErrorReporting(System.Int32 errorExitCode = 1)
     public CommandLineBuilder UseSuggestDirective()
@@ -83,7 +81,7 @@ public class CommandLineBuilder
     public CommandLineBuilder UseVersionOption(System.String name, System.String[] aliases)
   public class CommandLineConfiguration
     public static CommandLineBuilder CreateBuilder(Command rootCommand)
-    .ctor(Command command, System.Boolean enablePosixBundling = True, System.Boolean enableTokenReplacement = True, System.Func<System.CommandLine.Invocation.InvocationContext,System.CommandLine.Help.HelpBuilder> helpBuilderFactory = null, System.CommandLine.Parsing.TryReplaceToken tokenReplacer = null)
+    .ctor(Command command, System.Boolean enablePosixBundling = True, System.Boolean enableTokenReplacement = True, System.CommandLine.Parsing.TryReplaceToken tokenReplacer = null)
     public System.Collections.Generic.IReadOnlyList<Directive> Directives { get; }
     public System.Boolean EnablePosixBundling { get; }
     public System.Boolean EnableTokenReplacement { get; }

Alas, the .git/config change cannot be automatically cloned with the repository. Because of that, I don't think would be useful to add diff=api-contract to the distributed .gitattributes file, either.