A usual flow of a project (in my field) commonly looks like this:
having a result -> (1) writing a paper (with all the proofs) -> (2) making a conference version -> (3) uploading a full version to eprint -> (4) journal version
Usually, (2) is a shorter version of (1); and (3) is almost the same as (1) up to some changes that came up during the process of making (2); Yet, the work on (2) and (3) happens almost at the same time.
The question is how to deal with maintaining both versions (full + short) of the same paper.
So far I have been keeping two separate "papers", but this solutions has its problems: if you make a change to one (say, fixing a typo), you need to remember making the same change in the other one (which you usually forget).
What is the best strategy?