BUG: git prompt breaks with zsh < 5.0.6

From: Shupak, Vitaly <vitaly.shupak@deshaw.com>
Date: Jan 9, 2023, 17:12 UTC
Message-ID: <5807cdbe6d66427c9ff45ea78c2c1ffb@deshaw.com>

A change to git-prompt.sh in v2.38 to show presence of unresolved conflicts contains syntax which is not valid under zsh < 5.0.6. This version of zsh is old, but is still the default on RedHat 7 machines, for example.

The offending block is:

       local conflict="" # state indicator for unresolved conflicts
       if [[ "${GIT_PS1_SHOWCONFLICTSTATE}" == "yes" ]] &&
          [[ $(git ls-files --unmerged 2>/dev/null) ]]; then
               conflict="|CONFLICT"
       fi

[[ $(command) ]] syntax doesn't work in older version of zsh and should use [[ -n "$(command)" ]] instead.

Thanks, Vitaly