Created cleanup functionality for syncthing (#6884)

* Add clean up for Simple File Versioning pt.1

created test

* Add clean up for Simple File Versioning pt.2

Passing the test

* stuck on how javascript communicates with backend

* Add trash clean up for Simple File Versioning

Add trash clean up functionality of to allow the user to delete backups
after specified amount of days.

* Fixed html and js style

* Refactored cleanup test cases

Refactored cleanup test cases to one file and deleted duplicated code.

* Added copyright to test file

* Refactor folder cleanout to utility function

* change utility function to package private

* refactored utility function; fixed build errors

* Updated copyright year.

* refactor test and logging

* refactor html and js

* revert style change in html

* reverted changes in html and some js

* checkout origin head version edit...html

* checkout upstream master and correct file

lib/versioner/trashcan.go

@@ -56,51 +56,7 @@ func (t *trashcan) String() string {
 }
 
 func (t *trashcan) Clean(ctx context.Context) error {
-	if t.cleanoutDays <= 0 {
-		// no cleanout requested
-		return nil
-	}
-
-	if _, err := t.versionsFs.Lstat("."); fs.IsNotExist(err) {
-		return nil
-	}
-
-	cutoff := time.Now().Add(time.Duration(-24*t.cleanoutDays) * time.Hour)
-	dirTracker := make(emptyDirTracker)
-
-	walkFn := func(path string, info fs.FileInfo, err error) error {
-		if err != nil {
-			return err
-		}
-		select {
-		case <-ctx.Done():
-			return ctx.Err()
-		default:
-		}
-
-		if info.IsDir() && !info.IsSymlink() {
-			dirTracker.addDir(path)
-			return nil
-		}
-
-		if info.ModTime().Before(cutoff) {
-			// The file is too old; remove it.
-			err = t.versionsFs.Remove(path)
-		} else {
-			// Keep this file, and remember it so we don't unnecessarily try
-			// to remove this directory.
-			dirTracker.addFile(path)
-		}
-		return err
-	}
-
-	if err := t.versionsFs.Walk(".", walkFn); err != nil {
-		return err
-	}
-
-	dirTracker.deleteEmptyDirs(t.versionsFs)
-
-	return nil
+	return cleanByDay(ctx, t.versionsFs, t.cleanoutDays)
 }
 
 func (t *trashcan) GetVersions() (map[string][]FileVersion, error) {