Finding out which file belongs to which package in cygwin

Today, while trying to add some directories to the PATH variable in my startxwin.bat, I managed to corrupt the file.

I don't know what was wrong but the script refused to start the X server.

Well, I'll just recover the script by re-installing the package I thought.

The only problem is, I don't know which package the file belonged to! And I didn't want to re-install ALL the X packages of the X-server. That would have been the last resort, anyway.
A google search revealed that someone else had faced the same problem and cygwin had a package search which does the same thing; it can search within the packages.

I found the package and reinstalled it from the local copy on my HDD and all was well. X server started up as usual along with my customisations which I applied again.