The Diff Match and Patch libraries offer robust algorithms to perform the operations required for synchronizing plain text.
Diff * Compare two blocks of plain text and efficiently return a list of differences.
Match * Given a search string, find its best fuzzy match in a block of plain text. Weighted for both accuracy and location.
Patch * Apply a list of patches onto plain text. Use best-effort to apply patch even when the underlying text doesn't match.
This library implements Myer's diff algorithm which is generally considered to be the best general-purpose diff. A layer of pre-diff speedups and post-diff cleanups surround the diff algorithm, improving both performance and output quality.
The dart version of the code is being hosted at https://github.com/financeCoding/google-diff-match-patch for the time being.