difftastic

Difftastic is a structural diff tool that analyzes files based on their syntax tree rather than line-by-line comparison. It parses source code into abstract syntax trees (ASTs) and identifies changes at the syntactic level, which allows it to understand when code has been reformatted without actual logical changes and highlight only meaningful modifications.

The tool supports over 30 programming languages and integrates with git and other version control systems through configuration. When encountering files with unrecognized extensions or parse errors, it falls back to line-oriented diffing with word highlighting. Difftastic can also handle merge conflicts by parsing conflict markers and reconstructing the conflicting versions for comparison.

Difftastic uses Dijkstra's algorithm to solve structural diffing as a graph problem, but this approach has performance limitations on files with extensive changes and can consume significant memory. The tool provides a --check-only mode for quickly determining if two files have identical ASTs without generating visual output, and supports various configuration options through environment variables like DFT_PARSE_ERROR_LIMIT and DFT_BACKGROUND.