Only set prompt dir if it has not already been set. Useful for overriding from shell init files.
Only set prompt dir if it has not already been set. Useful for overriding from shell init files.

megalithic/zsh-git-prompt,wkentaro/zsh-git-prompt,mttrs/zsh-git-prompt,waltflanagan/zsh-git-prompt,megalithic/zsh-git-prompt,maebeale/.zsh-git-prompt,cevaris/zsh-git-prompt,aclissold/zsh-git-prompt,TheAtomicGoose/zsh-git-prompt,olivierverdier/zsh-git-prompt,biggerfisch/zsh-git-prompt,maebeale/.zsh-git-prompt,TheAtomicGoose/zsh-git-prompt,mttrs/zsh-git-prompt,sk1418/zsh-git-prompt,aclissold/zsh-git-prompt,sk1418/zsh-git-prompt,stepanv/zsh-git-prompt,olivierverdier/zsh-git-prompt,aclissold/zsh-git-prompt,TiddoLangerak/zsh-git-prompt,tasyrkin/zsh-git-prompt,biggerfisch/zsh-git-prompt,wkentaro/zsh-git-prompt,ToonSpin/zsh-git-prompt,atanasenko/zsh-git-prompt,TiddoLangerak/zsh-git-prompt,waltflanagan/zsh-git-prompt,ToonSpin/zsh-git-prompt,stepanv/zsh-git-prompt,cevaris/zsh-git-prompt,atanasenko/zsh-git-prompt,tasyrkin/zsh-git-prompt