fix: regenerate script toplevel resolution

[mrnossiom]

Hi 👋🏻,

I wanted to check on #870. (EDIT: sorry for linking the issue without a real connection)

When loading the regenerate_test_rustdocs.sh script, it would just output Generating rustdoc with: cargo 1.80.1 (376290515 2024-07-16) and then exit promptly. Upon closer examination, the TOPLEVEL variable would end up having two values, thus silently crashing the rest of the program.

Though my bash knowledge is limited, I think this is what is happening:

git rev-parse --show-toplevel 2>/dev/null || cd -- "$(dirname -- "${BASH_SOURCE[0]}" )" &>/dev/null && cd -- .. &>/dev/null && pwd
# is either (in git repo)
true || true && true && true # execs both git and pwd
false || true && true && true # execs only pwd

Wrapping the second part of the logical OR resolves the issue.

It seems that #856, introduced this and was recently committed.

[obi1kenobi]

Yup, I definitely messed that up — thank you so much!