Implement global --config-file and --diagnostic-output-directory options for dotnet test MTP

[Copilot]

This PR implements support for two "global" command-line options in dotnet test when using Microsoft Testing Platform (MTP). These options are processed by the dotnet CLI itself and properly transformed before being passed to individual test applications, rather than being blindly forwarded.

New Options Added

The following options are now available when using Microsoft Testing Platform:

• --config-file <CONFIG_FILE> - The testconfig.json configuration file to use for test execution
• --diagnostic-output-directory <DIAGNOSTIC_DIR> - Directory where diagnostic output will be placed

Implementation Details

The implementation follows the same pattern established by the existing --results-directory option (from #50081):

1. Path Transformation: Options that accept file/directory paths (--config-file, --diagnostic-output-directory) are automatically converted from relative to absolute paths using Path.GetFullPath() based on the current working directory.

2. Global Processing: These options are handled by the dotnet CLI and not included in the forwarded MSBuild arguments, ensuring they are processed consistently across all test projects.

3. Microsoft Testing Platform Only: The new options only appear when using Microsoft Testing Platform (determined by dotnet.config file with [dotnet.test.runner] name = Microsoft.Testing.Platform). VSTest continues to work unchanged.

Example Usage

# Enable Microsoft Testing Platform
echo -e "[dotnet.test.runner]\nname = Microsoft.Testing.Platform" > dotnet.config

# Use the new global options
dotnet test \
  --solution MySolution.sln \
  --config-file path/to/testconfig.json \
  --diagnostic-output-directory diagnostics \
  --results-directory TestResults

In this example, if run from /repo/root, the relative paths are transformed to:

• --config-file /repo/root/path/to/testconfig.json
• --diagnostic-output-directory /repo/root/diagnostics
• --results-directory /repo/root/TestResults

This ensures that all test projects receive absolute paths pointing to the same directories relative to where dotnet test was invoked, regardless of the individual project locations.

Testing

• Options appear correctly in dotnet test --help when using Microsoft Testing Platform
• Options are properly excluded from VSTest to maintain backward compatibility
• Path transformation handles both relative and absolute paths correctly
• Build passes without errors or warnings

Part of #49709.

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[Copilot]

Pull Request Overview

This PR implements support for two new "global" command-line options in dotnet test when using Microsoft Testing Platform (MTP): --config-file and --diagnostic-output-directory. These options are processed by the dotnet CLI and automatically converted to absolute paths before being forwarded to test applications.

Key changes:

• Added two new command-line options (--config-file and --diagnostic-output-directory) that only appear when using Microsoft Testing Platform
• Implemented path transformation logic that converts relative paths to absolute paths using Path.GetFullPath()
• Updated data structures and argument forwarding to handle the new options

Reviewed Changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Cli/dotnet/Commands/CliCommandStrings.resx	Added resource strings for the new command-line option descriptions and help names
src/Cli/dotnet/Commands/xlf/*.xlf	Updated localization files with new resource entries marked as "state=new"
src/Cli/dotnet/Commands/Test/TestingPlatformOptions.cs	Defined the two new command-line options with proper descriptions and arity
src/Cli/dotnet/Commands/Test/TestCommandParser.cs	Added the new options to the testing platform CLI command
src/Cli/dotnet/Commands/Test/Options.cs	Extended PathOptions record to include the new configuration file and diagnostic output directory paths
src/Cli/dotnet/Commands/Test/MSBuildUtility.cs	Implemented path transformation logic and updated PathOptions construction
src/Cli/dotnet/Commands/Test/TestApplication.cs	Added argument forwarding logic for the new options to test applications

Comments suppressed due to low confidence (1)

[Youssef1313]

@copilot Update the description to:

Specifies a testconfig.json file.