git git<tab> completes non-existent command `git gitk`

From: Anthony Sottile <asottile@umich.edu>
Date: May 23, 2020, 22:25 UTC
Message-ID: <CA+dzEBnpheB-ZT5+bajKphux-+7gYFx1Msws7mXM=LOJO7pukw@mail.gmail.com>

easiest to reproduce is with docker

```dockerfile
FROM ubuntu:focal
RUN : \
    && apt-get update \
    && DEBIAN_FRONTEND=noninteractive apt-get install -y
--no-install-recommends \
        bash-completion \
        git \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/*
```

```console $ docker run --rm -ti test bash root@23e691ecc7ba:/# [ -f /etc/bash_completion ] && . /etc/bash_completion root@23e691ecc7ba:/# git gitk ```

(I typed git git<tab>)

```console $ git gitk git: 'gitk' is not a git command. See 'git --help'. ```

this is a bit annoying because I have some aliases/commands for git-github-*

the git version I have is 2.25.1:

```console $ git --version git version 2.25.1 ```

Anthony