add script for checking thread locks in funcs that call MakeGitError

Makefile

@@ -4,6 +4,7 @@ build-libgit2:
 	./script/build-libgit2-static.sh
 
 test: build-libgit2
+	go run script/check-MakeGitError-thread-lock.go
 	./script/with-static.sh go test ./...
 
 install: build-libgit2

script/check-MakeGitError-thread-lock.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/printer"
+	"go/token"
+	"log"
+	"strings"
+)
+
+var (
+	fset = token.NewFileSet()
+)
+
+func main() {
+	log.SetFlags(0)
+
+	bpkg, err := build.ImportDir(".", 0)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	pkgs, err := parser.ParseDir(fset, bpkg.Dir, nil, 0)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for _, pkg := range pkgs {
+		if err := checkPkg(pkg); err != nil {
+			log.Fatal(err)
+		}
+	}
+	if len(pkgs) == 0 {
+		log.Fatal("No packages to check.")
+	}
+}
+
+var ignoreViolationsInFunc = map[string]bool{
+	"MakeGitError":  true,
+	"MakeGitError2": true,
+}
+
+func checkPkg(pkg *ast.Package) error {
+	var violations []string
+	ast.Inspect(pkg, func(node ast.Node) bool {
+		switch node := node.(type) {
+		case *ast.FuncDecl:
+			var b bytes.Buffer
+			if err := printer.Fprint(&b, fset, node); err != nil {
+				log.Fatal(err)
+			}
+			src := b.String()
+
+			if strings.Contains(src, "MakeGitError") && !strings.Contains(src, "runtime.LockOSThread()") && !strings.Contains(src, "defer runtime.UnlockOSThread()") && !ignoreViolationsInFunc[node.Name.Name] {
+				pos := fset.Position(node.Pos())
+				violations = append(violations, fmt.Sprintf("%s at %s:%d", node.Name.Name, pos.Filename, pos.Line))
+			}
+		}
+		return true
+	})
+	if len(violations) > 0 {
+		return fmt.Errorf("%d non-thread-locked calls to MakeGitError found. To fix, add the following to each func below that calls MakeGitError, before the cgo call that might produce the error:\n\n\truntime.LockOSThread()\n\tdefer runtime.UnlockOSThread()\n\n%s", len(violations), strings.Join(violations, "\n"))
+	}
+	return nil
+}