lib/versioner: Minor fixes in comments and error message (#9031)

* lib/versioner: Factor out DefaultPath constant.

Replace several instances where .stversions is named literally to all
use the same definition in the versioner package.  Exceptions are the
packages where a cyclic dependency on versioner is impossible, or some
tests which combine the versions base path with other components.

* lib/versioner: Fix comment about trash can in simple versioner.

* lib/versioner: Fix wrong versioning type string in error message.

The error message shows the folder type instead of the versioning
type, although the correct field is used in the comparison.

lib/model/model.go

@@ -399,7 +399,7 @@ func (m *model) addAndStartFolderLockedWithIgnores(cfg config.FolderConfiguratio
 	// These are our metadata files, and they should always be hidden.
 	ffs := cfg.Filesystem(nil)
 	_ = ffs.Hide(config.DefaultMarkerName)
-	_ = ffs.Hide(".stversions")
+	_ = ffs.Hide(versioner.DefaultPath)
 	_ = ffs.Hide(".stignore")
 
 	var ver versioner.Versioner

lib/model/model_test.go

@@ -2647,7 +2647,7 @@ func TestVersionRestore(t *testing.T) {
 			file = filepath.FromSlash(file)
 		}
 		tag := version.In(time.Local).Truncate(time.Second).Format(versioner.TimeFormat)
-		taggedName := filepath.Join(".stversions", versioner.TagFilename(file, tag))
+		taggedName := filepath.Join(versioner.DefaultPath, versioner.TagFilename(file, tag))
 		fd, err := filesystem.Open(file)
 		if err != nil {
 			t.Error(err)
@@ -2680,7 +2680,7 @@ func TestVersionRestore(t *testing.T) {
 		}
 		for _, version := range versions {
 			if version.VersionTime.Equal(beforeRestore) || version.VersionTime.After(beforeRestore) {
-				fd, err := filesystem.Open(".stversions/" + versioner.TagFilename(file, version.VersionTime.Format(versioner.TimeFormat)))
+				fd, err := filesystem.Open(versioner.DefaultPath + "/" + versioner.TagFilename(file, version.VersionTime.Format(versioner.TimeFormat)))
 				must(t, err)
 				defer fd.Close()