Tolerate .git directory when checking if dir is empty

Many users will be running version control; we should ignore .git
directories also therefore.

pkg/plugins/golang/v3/init.go

@@ -184,9 +184,16 @@ func checkDir() error {
 			if err != nil {
 				return err
 			}
+			// Allow the whole .git directory tree
+			if info.Name() == ".git" {
+				return filepath.SkipDir
+			}
+			// Also allow go.mod and dot-files
 			if info.Name() != "go.mod" && !strings.HasPrefix(info.Name(), ".") {
 				return fmt.Errorf(
-					"target directory is not empty (only go.mod and files with the prefix \".\" are allowed); found existing file %q",
+					"target directory is not empty "+
+						"(only go.mod, files with the prefix \".\" and .git directories are allowed); "+
+						"found existing file %q",
 					path)
 			}
 			return nil