Wrong Git head reported

[Rudloff]

Checklist

• I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2020.07.28
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• I've searched the bugtracker for similar bug reports including closed ones
• I've read bugs section in FAQ

Verbose log

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2020.07.28
[debug] Git HEAD: 3ba720d
[debug] Python version 2.7.16 (CPython) - Linux-4.19.0-9-amd64-x86_64-with-debian-10.4
[debug] exe versions: ffmpeg 4.1.6-1, ffprobe 4.1.6-1, rtmpdump 2.4
[debug] Proxy map: {}
Usage: __main__.py [OPTIONS] URL [URL...]

__main__.py: error: You must provide at least one URL.
Type youtube-dl --help to see a list of all options.

Description

When running youtube-dl from within another project, -v will report the Git head of the parent project.
This can make bug reports confusing (see #16136 (comment)).

Maybe the Git head should only be fetched if youtube-dl is at the root of the Git project?

Steps to reproduce :

mkdir foo
cd foo/
git init
git commit --allow-empty -m "Foo"
wget https://github.com/ytdl-org/youtube-dl/archive/2020.07.28.zip
unzip 2020.07.28.zip
python youtube-dl-2020.07.28/youtube_dl/__main__.py -v