TeamCity 7.1: Checkout Rule + Mecurial doesn't work

I have a Mecurial VCS Root with several sub-folders containing code for different builds:


/Frontend/Android
/Frontend/IOS
/Frontend/WP



There're 3 Build Configs for them respectively and I want each to be triggered only when code in the correct folder changes. I have tried the following:

- Using VCS Trigger Rule: it works, but it shows the non-triggering code as pending changes so I don't want to use it.

- Using VCS Checkout Rule: this seems to be the obvious solution but in fact it still get all the code of the whole repo, below is my checkout rule for 1 of the build config



-:.
+:Frontend/Android


And VCS Checkout Mode is always 'Automatically on Server'


Is there something wrong with my steps? Or is it a bug (with Checkout Rule + Mecurial)?





Environment info
TeamCity Professional 7.1 (build 23907)
Windows 7