You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: changetracker.rs
    path of file: ./repos/anki/rslib/src/sync/media/database/client
    
    the code of the file until where you have to start completion: // Copyright: Ankitects Pty Ltd and contributors
// License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html

use std::collections::HashMap;
use std::path::Path;
use std::time;

use anki_io::read_dir_files;
use tracing::debug;

use crate::media::files::filename_if_normalized;
use crate::media::files::mtime_as_i64;
use crate::media::files::sha1_of_file;
use crate::media::files::NONSYNCABLE_FILENAME;
use crate::prelude::*;
use crate::sync::media::database::client::MediaDatabase;
use crate::sync::media::database::client::MediaEntry;
use crate::sync::media::MAX_INDIVIDUAL_MEDIA_FILE_SIZE;

struct FilesystemEntry {
    fnam
    
    pub(crate) fn register_changes(&mut self, ctx: &MediaDatabase) -> Result<()> {
        ctx.transact(|ctx| {
            // folder mtime unchanged?
            let dirmod = mtime_as_i64(self.media_folder)?;

            let mut meta = ctx.get_meta()?;
            debug!(
                folder_mod = dirmod,
                db_mod = meta.folder_mtime,
                "begin change check"
            );
            if dirmod == meta.folder_mtime {
                debug!("skip check");
                return Ok(());
            } else {
                meta.folder_mtime = dirmod;
            }

            let mtimes = ctx.all_mtimes()?;
            self.checked += mtimes.len();
            self.fire_progress_cb()?;

            let (changed, removed) = self.media_folder_changes(mtimes)?;

            self.add_updated_entries(ctx, changed)?;
            self.remove_deleted_files(ctx, removed)?;

            ctx.set_meta(&meta)?;

            // unconditional fire at end of op for accurate counts
            self.fire_progress_cb()?;

            Ok(())
        })
    }