I've previously installed some packages from .deb files using gdeb. I've now forgotten which ones. As I will soon update from Precise to Trusty, I'd like to uninstall them & go back to the standard Precise repo ones before upgrading: then I will find out if apps dependent on these packages work before considering installing them from .deb files. I think that I remember that this could be done using Synaptic. Anybody know how?