Related: https://github.com/ohmyzsh/ohmyzsh/pull/10713/files#r820219899

When the `git init` call fails, the directory is not created,
so the rm command fails with a not found error. This change
checks whether the directory exists before deleting it.

The previous check simply compared whether the last commit of the branch
was the same in the local and the remote repository.

This commit also checks whether the remote commit is an ancestor of the
local commit. This fixes the case where the local repository has new
commits after the last published commit.

Fixes #10680

Reference: https://www.zsh.org/mla/users/2022/msg00067.html

Co-authored-by: Philippe Troin <phil@fifi.org>

Fixes #9699

Fixes missing $USER value in ArchLinux sh (bash)

Fixes #10587

The previous check only worked if the user could run `sudo` without typing the
password, which is almost none (I checked in Google Cloud Shell so I failed to
notice this).

This new check works whether the user has no sudo privileges, or if it has,
whether they have to type in the password or not.

It should really be easier to check if the user doesn't have privilege without
having to make them type the password.

This fixes the error in Google Cloud Shell, where a password prompt
appears when running `chsh` but the user (hello) does not have a
password.

If ran with `sudo`, the `chsh` command happens without a password
prompt.

Fixes #10448

Fixes #10422

Fixes #10404

Co-authored-by: Marc Cornellà <hello@mcornella.com>