robbyrussell/oh-my-zsh — pull request #2740 by docwhat (2014-04-23 04:37:50+00:00)
Title: Don't override ZSH_COMPDUMP if already set.

This allows customization via .zshenv if wanted. This is helpful for zsh
developers and people who want to move it out of $HOME

For example, developers may want to have granularity higher than just the version.