Riff, the Refining Diff

Riff is a wrapper around diff that highlights which parts of lines have changed.

Much like git, Riff sends its output to a pager, trying these in order:

1. Whatever is specified in the $PAGER environment variable
2. moar because it is nice
3. less because it is ubiquitous

Usage

git diff | riff

Or if you do...

git config --global pager.diff riff git config --global pager.show riff git config --global pager.log riff git config --global interactive.diffFilter riff

... then all future git diff, git show and git log --patch output will be refined.

Or you can use riff as an alias for diff:

riff file1.txt file2.txt

Installation

With Homebrew

brew install riff

From the Rust Crate

cargo install riffdiff

Manual Install

1. Go here and download the correct binary for your platform

   • If no binary exists for your platform, please report it

2. chmod a+x riff-*

3. mv riff-* /usr/local/bin/riff
4. Optionally followed by this to have riff highlight git output by default:

git config --global pager.diff riff git config --global pager.show riff git config --global pager.log riff git config --global interactive.diffFilter riff

See Also

This VSCode extension for improved Git commit message editing is nice. Yes, I wrote it and I'm tooting my own horn here.

Good choice if you (like me!) are using VSCode for Git commit message editing.

Development

If you put example input and output in the testdata directory, then cargo test will verify that they match.

Invoke ci.sh to run the same thing as CI.

Invoke benchmark.py to get numbers for how fast your current source code is versus earlier releases.

Invoke git log -p | cargo run -- to demo highlighting.

Making a new release

Just invoke ./release.sh and follow instructions.

If you want to test the release script without actually releasing anything, do:

./release.sh --dry

TODO

Misc

• Render ESC characters in the diff as Unicode ␛
• --help: Only print installing-into-$PATH help if we aren't already being executed from inside of the $PATH
• Do git show 5e0a1b2b13528f40299e78e3bfa590d9f96637af and scroll to the end. How should we visualize the reformatting of the No-newline-at-eof code?
• Do git show 0f5dd84 and think about how to visualize one line changing to itself with a comma at the end plus a bunch of entirely new lines. Think of a constant array getting one or more extra members.
• Do git show -b 77c8f77 and think about what rule we should use to highlight the leading spaces of the + refined and + page lines at the end of the file.
• Do git show 57f27da and think about what rule we should use to get the REVERSE vs reversed() lines highlighted.
• Add test for never changing the number of lines in the input, that messes up git add -p behavior.
• Think about how to visualize an added line break together with some indentation on the following line.
• Make sure we highlight the output of git show --stat properly
• Make sure we can handle a git conflict resolution diff. File format is described at http://git-scm.com/docs/git-diff#combineddiff_format.
• Given three files on the command line, we should pass them and any options on to diff3 and highlight the result

TODO future

• Detect moved blocks and use a number as a prefix for both the add and the remove part of the move. Hightlight any changes just like for other changes.

DONE

• Make a main program that can read input from stdin and print it to stdout.
• Make the main program identify different kinds of lines by prefix and color them accordingly. Use the same color scheme as git.
• Make the main program identify blocks of lines that have been replaced by another block of lines.
• Make the Refiner not highlight anything if either old or new is empty
• Use https://crates.io/crates/diffus to refine hunks
• Build refined hunks and print them
• Highlight ^diff, ^index, ^+++ and ^--- lines in bold white
• Prefix all added / removed lines with the correct ANSI color code
• Don't highlight the initial + / - on added / removed lines
• Make sure we get the linefeeds right in diffs, try git show 28e074bd0fc246d1caa3738432806a94f6773185 with and without riff.
• Visualize added line endings
• Visualize removed line endings
• Visualize removed linefeed at end of file properly
• Visualize adding a missing linefeed at end of file properly
• Visualize missing linefeed at end of file as part of the context properly
• Refine ax->bx\nc properly
• Strip all color from the input before handling it to enable users to set Git's pager.diff and pager.show variables to 'riff' without also needing to set color.diff=false.
• If stdout is a terminal, pipe the output to a pager using the algorithm described under core.pager in git help config.
• You can do git diff | riff and get reasonable output.
• Do not highlight anything if there are "too many" differences between the sections. The point here is that we want to highlight changes, but if it's a replacement rather than a change then we don't want to highlight it.
• Refine by word rather than by character
  • Test case git show 2ac5b06: Should highlight all of both some and one or.
• Do some effort to prevent fork loops if people set $PAGER to riff
• Add support for --help
• Add support for --version
• Print help and bail if stdin is a terminal
• On exceptions, print the current version just like --version
• On exceptions, print a link to the issue tracker
• Add test case verifying that the Inspired by part of git show 77c8f77 -- bin/riff is highlighted as an upside down L.
• Find out how the LCS algorithm scales and improve the heuristic for when not to call it.
• Tune the upper bound on how large regions we should attempt to refine
• Make a CI script
• Set up CI calling the CI script
• Document ci.sh's existence
• Figure out cross compiling to Linux and macOS ARM (look into cross which uses Docker for cross compiling)
• Make a release script
• Document release.sh's existence
• Verify that the Linux binary works
• Document install instructions
• Make a public release
• Remedy release.sh FIXMEs
• Add a trailing whitespace analysis pass to the Refiner
• Let the Refiner highlight whitespace errors among the added lines in reverse red.
• Highlight whitespace in added parts only
• Add highlighting of non-leading tabs to the whitespace analysis
• Profile and see if we can go faster
• In ci.sh, add a test case verifying that our exception handler prints backtraces in release builds (should fail when stripping the release binary)
• In ci.sh, add a test case verifying that our exception handler prints line numbers for the riff frames in the backtraces, in release builds. This should fail when stripping the release binary.
• Require line numbers in backtraces in release builds
• Make the Linux binary smaller
• Put argv contents in crash report
• Handle plain non-git diff files
• Given two files on the command line, we should pass them on to diff and highlight the result.
• Support riff -b path1 path2 to diff files ignoring whitespace
• Bound how-much-to-highlight restriction by number of characters highlighted rather than by number of tokens highlighted
• Get ourselves some kind of benchmark suite / example(s)