complete -f -c git -n "__fish_git_using_command submodule; and not __fish_seen_subcommand_from $submodulecommands" -a 'sync' -d 'Sync submodules\' URL with .gitmodules'
complete -f -c git -n "__fish_git_using_command submodule; and not __fish_seen_subcommand_from $submodulecommands" -s q -l quiet -d "Only print error messages"
The \' is still recognized as a single quote by the highlighter, causing it to highlight Sync submodules\ as string, and then everything after gitmodules' (including the entire next line) as a string again.
From the git completion script:
The
\'
is still recognized as a single quote by the highlighter, causing it to highlightSync submodules\
as string, and then everything aftergitmodules'
(including the entire next line) as a string again.