Three Way Merge Algorithms for Text

Question

So I\'ve been working on a wiki type site. What I\'m trying to decide on is what the best algorithm for merging an article that is simultaneously being edited by two users.

Answer 1

Frankly, I'd rely on diff3. It's on pretty much every Unix distro, and you can always build and bundle an .EXE for Windows to ensure it is there for your purposes.

Answer 2

Bill Ritcher's excellent paper "A Trustworthy 3-Way Merge" talks about some of the common gotchas with three way merging and clever solutions to them that commercial SCM packages have used.

The 3-way merge will automatically apply all the changes (which are not overlapping) from each version. The trick is to automatically handle as many almost overlapping regions as possible.

Answer 3

There's a formal analysis of the diff3 algorithm, with pseudocode, in this paper: http://www.cis.upenn.edu/~bcpierce/papers/diff3-short.pdf

It is titled "A Formal Investigation of Diff3" and written by Sanjeev Khanna, Keshav Kunal, and Benjamin C. Pierce from Yahoo.