feat: support external test packages in go

[not-matthias]

Fixes #23

Lots of changes required, because external test packages are quite different:

• Added an example that reproduces the error
• Added more tests for the benchmark discovery
• Support external tests by moving them to the codspeed/ repository

[Copilot]

Pull Request Overview

Add support for external Go test packages (packages with the _test suffix) in discovery, patching, templating, and build flow to fix missing benchmark discovery and execution (Fixes #23).

• Discovery: Detect and handle external test packages; surface is_external and select correct files/imports/paths.
• Build pipeline: Patch package declarations only where needed, move/rename external test files into a codspeed sub-package, and update the runner template to call unqualified functions for external tests.
• Tests/fixtures: Add a new example project using external test packages and update integration and discovery snapshots accordingly.

Reviewed Changes

Copilot reviewed 37 out of 37 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
go-runner/testdata/projects/example-with-test-package/math_test.go	Add external test package benchmarks for math package
go-runner/testdata/projects/example-with-test-package/math.go	Add simple math package used by external tests
go-runner/testdata/projects/example-with-test-package/go.mod	New module for the example project
go-runner/testdata/projects/example-with-test-package/fib_external/fib_test.go	Add internal tests in separate directory
go-runner/testdata/projects/example-with-test-package/fib_external/fib_integration_test.go	Add external test package tests + benchmark
go-runner/testdata/projects/example-with-test-package/fib_external/fib.go	Fibonacci implementation for tests
go-runner/testdata/projects/example-with-test-package/fib/fib_test.go	Internal tests and benchmarks
go-runner/testdata/projects/example-with-test-package/fib/fib_integration_test.go	External test package tests
go-runner/testdata/projects/example-with-test-package/fib/fib.go	Fibonacci implementation for tests
go-runner/testdata/projects/example-with-test-package/README.md	Document the external test package scenario
go-runner/src/snapshots/codspeed_go_runner__integration_tests__assert_results_snapshots@zerolog.snap	Update integration results snapshot for zerolog
go-runner/src/snapshots/codspeed_go_runner__integration_tests__assert_results_snapshots@zap.snap	Update integration results snapshot for zap
go-runner/src/snapshots/codspeed_go_runner__integration_tests__assert_results_snapshots@opentelemetry-go.snap	Update integration results snapshot for opentelemetry-go
go-runner/src/snapshots/codspeed_go_runner__integration_tests__assert_results_snapshots@hugo.snap	Update integration results snapshot for hugo
go-runner/src/snapshots/codspeed_go_runner__integration_tests__assert_results_snapshots@example-with-test-package.snap	New snapshot asserting external test package results
go-runner/src/integration_tests.rs	Add new integration test case for example-with-test-package
go-runner/src/builder/templater.rs	Handle external test packages: patch package decls, move/rename test files, install dep, generate runner in codspeed subdir
go-runner/src/builder/template.go	Template changes to import only internal tests and call unqualified names for external tests
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@zerolog.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@zap.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@opentelemetry-go.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@hugo__identity.snap	New discovery snapshot segment
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@hugo__common__htime.snap	New discovery snapshot segment
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@hugo.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@golang-benchmarks.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@fzf.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@fuego.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@example.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@example-with-test-package.snap	New discovery snapshot for test package example
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@example-with-main.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@example-with-helper.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@example-with-dot-go-folder.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@cli-runtime.snap	Update discovery snapshot
go-runner/src/builder/snapshots/codspeed_go_runner__builder__discovery__tests__discover_benchmarks@caddy.snap	Update discovery snapshot
go-runner/src/builder/patcher.rs	Split import patching vs package patching; add install_codspeed_dependency; add helpers to patch specific files or dir
go-runner/src/builder/mod.rs	Build the whole codspeed package directory instead of a single file
go-runner/src/builder/discovery.rs	Detect external test packages, select proper file/import lists, include is_external in benchmarks

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[codspeed-hq]

CodSpeed Performance Report

Merging #26 will not alter performance

_{Comparing cod-1505-support-external-test-packages-in-go (9532997) with main (90629b1)}

Summary

✅ 24 untouched

[art049]

lot of changes but looks good, and makes sense!