bat prepends the arguments from its config file to the command line, so a
user who has `--show-all` in their config and also types `-A` passes the
flag twice, and clap rejects that with "the argument '--show-all' cannot be
used multiple times" and exit code 2. The file is never displayed.
`--plain`, `--number`, `--number-nonblank`, `--force-colorization` and
`--no-paging` already avoid this by overriding themselves. The same is now
done for the eight remaining flags that affect how a file is displayed:
--show-all, --diff, --chop-long-lines, --squeeze-blank, --unbuffered,
--quiet-empty, --no-custom-assets and --set-terminal-title.
Repeating a flag produces byte-identical output to giving it once, and
--show-all still conflicts with --language as before.
