Comparison to see if updates are available

Can anyone tell we where the comparison is made by WordPress to see if an update is available for a particular theme?

I kinda assume it’s a simple matter of checking version numbers – if you have version 1.2.3 installed, it compares “1.2.3” with the latest version of a theme available and if that is “1.2.4” or higher, there’s an update available. (Or am I completely wrong on that assumption??)

I want to find where it checks the version no. of my installed theme so that I can change it to the latest update number. Reason being I don’t want to update my theme right now but I do want to dismiss the notice AND be told when an even newer update is available, so I can make the decision again. Solutions I’ve found seem to revolve around permanently disabling the ‘update available’ notice – albeit I’ve investigated plugins rather than themes, I’m again just assuming the same will apply. On that note, can anyone also tel me the same thing for plugins?

Or if I’m completely wrong in my assumptions, anyone able to set me straight?