On Ubuntu 20.04.3 LTS, I use the following git version installed from
its apt repository:

$ git --version
git version 2.25.1

I find that there are some  sub-commands can't be completed by TAB key:

$ git <TAB>
add               cherry-pick       fetch             latexdiff
 pull              restore           status
am                citool            format-patch      log
 push              revert            submodule
apply             clean             fsck              merge
 range-diff        rm                switch
archive           clone             gc                mergetool
 rebase            send-email        tag
bisect            commit            gitk              mv
 reflog            shortlog          whatchanged
blame             config            grep              nbdiffdriver
 remote            show              worktree
branch            deborig           gui               nbdifftool
 repack            show-branch
bundle            describe          help              nbmergedriver
 replace           sparse-checkout
checkout          diff              init              nbmergetool
 request-pull      stage
cherry            difftool          instaweb          notes
 reset             stash

As you can see, there are some sub-commands which are not listed in
the above list, for example, the following ones:

$ git ls-remote
$ git ls-files

Any hints for this problem?

Regards
-- 
Assoc. Prof. Hongyi Zhao [off-list ref]
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
No. 473, Quannan West Street, Xindu District, Xingtai, Hebei province