basically time + file size change + boost - fatigue calculated on local + server
there comes some factors
ignored by scm? is it a programming language?
when was last file modification
how long the user keep coding(too long means bad)
does the file modification event came from user action?(doesn't count massive file change in short duration like compiling)
user item + title boost
We will open source it when the time comes.
You can help us if the formula isn't right! ;)