Currently MacHg auto-completes the directory name when cloning a repository. However, this is quite annoying as it immediately complains about the existing directory. Furthermore because of this feature one can't enter a directory similar to an existing.
For example in my case I wanted to clone a repository to an existing directory. However, MacHg didn't let me do this. So I went and renamed the exising directory from "wp-content" to "wp-content2". Now, when I tried to clone the repository to "wp-content" MacHg always wanted to auto-complete the path to "wp-content2" and there seems to be no way (other than renaming "wp-content2" to something completely different) to convince MacHg to take "wp-content" as destination path.