Why does glibc provide bash?

[Andy Wingo <wingo@igalia.com>]

Hi,

Let's start bash with no RC file in a null environment:

    $ env -i ~/.guix-profile/bin/bash --norc

Check to make sure the env is empty:

    bash-4.3$ env
    PWD=/home/wingo
    SHLVL=1
    _=/usr/bin/env

Now look at this little sample file:

    bash-4.3$ .guix-profile/bin/cat /tmp/foo.bash
    _foo_complete ()
    {
        false
    }

    complete -F _foo_complete foo

OK now we run bash on that file:

    bash-4.3$ .guix-profile/bin/bash --norc /tmp/foo.bash
    /tmp/foo.bash: line 6: complete: command not found

What could be going on?  Well here's a lollerskates thing, back in the
main environment:

    $ ls -l `which bash`
    lrwxrwxrwx 11 root guixbuild 63 Jan  1  1970 /home/wingo/.guix-profile/bin/bash -> /gnu/store/5995q4p9ayvicd8qxjmn8zrwis4y7a8c-glibc-2.21/bin/bash

It's coming from glibc!!!  Zomg.  Why is this?  From what I can tell
it's not in the propagated inputs of glibc, so this shouldn't be
happening.

Andy