exit.
    -no-obsolete
           Drop all obsolete strings.
    -extensions <ext>[,<ext>]...
           Process files with the given extensions only.
           The extension list must be separated with commas, not with whitespace.
           Default: '%1'.
    -pluralonly
           Only include plural form messages.
    -silent
           Do not explain what is being done.
    -no-sort
           Do not sort contexts in TS files.
    -no-recursive
           Do not recursively scan the following directories.
    -recursive
           Recursively scan the following directories (default).
    -I <includepath> or -I<includepath>
           Additional location to look for include files.
           May be specified multiple times.
    -locations {absolute|relative|none}
           Specify/override how source code references are saved in TS files.
           Default is absolute.
    -no-ui-lines
           Do not record line numbers in references to UI files.
    -disable-heuristic {sametext|similartext|number}
           Disable the named merge heuristic. Can be specified multiple times.
    -pro <filename>
           Name of a .pro file. Useful for files with .pro file syntax but
           different file suffix. Projects are recursed into and merged.
    -pro-out <directory>
           Virtual output directory for processing subsequent .pro files.
    -source-language <language>[_<region>]
           Specify the language of the source strings for new files.
           Defaults to POSIX if not specified.
    -target-language <language>[_<region>]
           Specify the language of the translations for new files.
           Guessed from the file name if not specified.
    -ts <ts-file>...
           Specify the output file(s). This will override the TRANSLATIONS
           and nullify the CODECFORTR from possibly specified project files.
    -codecfortr <codec>
           Specify the codec assumed for tr() calls. Effective only with -ts.
    -version
           Display the version of lupdate and exit.
    @lst-file
           Read additional file names (one per line) or includepaths (one per
           line, and prefixed with -I) from lst-file.