At least one user has a slight confusion on how subrepositories worked and added one by drag/dropping their local subrepo checkout into the parent, then when adding the subrepo used that same local path for both the source and the relative destination. In their case this caused locking problems in hg, but more generally if they'd tried to share that parent repo with others, the subrepos would not have been available to clone. The source path should almost always be a remote clone (although we allow browsing the file system for people that use it for unusual cases, like local-only setups or file share remotes).

We should add some validation here so that the source path is not allowed to be a subfolder of the parent.

Original issue: https://answers.atlassian.com/questions/109288/always-waiting-on-lock-on-subrepository