from(['./foo', './bar/*.ts', './baz.html'])
    .pipe(
        setAll('pattern'),
        mergeSet('filePath', ({ pattern }) => getFileList(pattern)),
        set('outFilePath', ({ filePath }) => resolve(filePath)),
        mergeSet('isSuccess', ({ filePath, outFilePath }) => upgradeFile(filePath, outFilePath)),
        scanSet('counter', (acc, { pattern }) => {
            const index = acc[pattern] || 0;
            return ({ ...acc, [pattern]: index + 1 });
        }, {} as Record<string, number>),
    )
    .subscribe(({ pattern, filePath, outFilePath, isSuccess, counter }) => {
        // ...
    });