feat: use GIT_ASKPASS with git clone so tokens do not appear in log messages

[zot]

use GIT_ASKPASS to hide token from log messages

[zot]

Tested this locally:

This should ask for a password and it does:

julia> run(`git clone https://github.com/zot/DemoRegistry`)
Cloning into 'DemoRegistry'...
fatal: cannot exec '/usr/bin/ksshaskpass': No such file or directory
Username for 'https://github.com': 

This does not ask for a password, runs properly, and does not log the token:

julia> u="https://zot:<TOKEN>@github.com/zot/DemoRegistry"
julia> runwithpasswd(u) do url, env; run(Cmd(`git clone $url`; env)); end
Cloning into 'DemoRegistry'...
remote: Enumerating objects: 19, done.
remote: Counting objects: 100% (2/2), done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 19 (delta 0), reused 0 (delta 0), pack-reused 17 (from 1)
Receiving objects: 100% (19/19), done.
Resolving deltas: 100% (2/2), done.
Process(setenv(`git clone https://github.com/zot/DemoRegistry`,["GIT_ASKPASS=/tmp/jl_zNIlE8"]), ProcessExited(0))

[vdayanand]

LGTM