No, Git does not store this information. Let's check what it does in fact store:
$ git init
Initialized empty Git repository in /home/user/test/.git/
$ echo 'this is a file' > README
$ git add README
$ git commit -m 'Initial commit'
[master (root-commit) 8a4399d] Initial commit
1 file changed, 1 insertion(+)
create mode 100644 README
$ git cat-file -p 8a4399d
tree dbf49a0436d9fe83cc1528362959563c5b230ac4
author A Uthor <author@example.com> 1668115302 +0100
committer A Uthor <author@example.com> 1668115302 +0100
Initial commit
That's all that's stored in a Git commit. If it is not the root commit, it will have an additional "parent" line.
As for GitHub: you can use Git without it. It is only contacted when you run git push
or git fetch
. We can't see their source code, so we don't know. Probably, as part of webserver logs, at least IP address. Not sure what you mean with "system details", but probably not.