tools: Fix incompatible dependencies for new Gitaly linter

In d1c74493a (Add golangci-lint custom linter infrastructure,
2023-02-15), we have added a Gitaly-specific custom linter that is
plugged into golangci-lint. For the time being, we agreed to just make
it use the same `go.mod` as the main module, mostly because we wanted
`make test` to also execute its tests.

This is causing problems already, though. The Renovate bot has decided
to immediately try and upgrade the new dependency on golang.org/x/tools
to the most recent version. But this causes CI failures now because
golangci-lint requires all plugins to always use the same version of
that package as it uses itself.

Fix this by moving the Gitaly-specific linting infrastructure into a
subpackage of `tools/golangci-lint` and make it reuse the `go.mod` file.
This ensures that they always use compatible versions and that the main
production-level `go.mod` file is not tied to a specific dependency
version.

1 files changed, 29 insertions, 0 deletions

diff --git a/tools/golangci-lint/gitaly/lint.go b/tools/golangci-lint/gitaly/lint.go
new file mode 100644
index 000000000..f03e118eb
--- /dev/null
+++ b/tools/golangci-lint/gitaly/lint.go
@@ -0,0 +1,29 @@
+package main
+
+import (
+	"golang.org/x/tools/go/analysis"
+)
+
+type analyzerPlugin struct{}
+
+func (*analyzerPlugin) GetAnalyzers() []*analysis.Analyzer {
+	return []*analysis.Analyzer{
+		NewQuoteInterpolationAnalyzer([]string{
+			"fmt.*",
+		}),
+		NewErrorWrapAnalyzer([]string{
+			"fmt.Errorf",
+			"gitlab.com/gitlab-org/gitaly/v15/internal/structerr.*",
+		}),
+	}
+}
+
+// AnalyzerPlugin is a convention of golangci-lint to implement a custom linter. This variable
+// must implement `AnalyzerPlugin` interface:
+//
+//	type AnalyzerPlugin interface {
+//		GetAnalyzers() []*analysis.Analyzer
+//	}
+//
+// For more information, please visit https://golangci-lint.run/contributing/new-linters/
+var AnalyzerPlugin analyzerPlugin