/usr/share/fish/completions/command.fish is in fish-common 2.4.0-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | complete -c command -s h -l help --description 'Display help and exit'
complete -c command -s s -l search --description 'Print the file that would be executed'
complete -c command --description "Command to run" -xa "(__fish_complete_subcommand)"
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