Ydiff is a terminal-based tool to view colored, incremental diffs in a version-controlled workspace or from stdin, in side-by-side (similar to diff -y) or unified mode, and auto-paged. It only requires Python >= 3.3 without external dependencies and less as a pager.

The diffs in side-by-side mode appear below. See also the screenshots of the unified mode.

Theme "default" on a dark terminal background:

Theme "default" on a light terminal background:

Theme "dark" on a dark terminal background:

Theme "light" on a light terminal background:

Ydiff only depends on Python built-in libraries, so you can just download the source and run without worrying about any installation. Git tagged revisions will be packaged and uploaded to PyPI timely, however, packages hosted elsewhere are not (please note they are not managed by the author @ymattw).

To run from source directly, just save ydiff.py as ydiff to whatever directory which is in your $PATH, for example, $HOME/bin:

curl -L https://raw.github.com/ymattw/ydiff/master/ydiff.py > ~/bin/ydiff
chmod +x ~/bin/ydiff

To install from PyPI:

pip install --upgrade ydiff

To install with Homebrew (Formula) on macOS:

brew install ydiff

To install on Fedora:

dnf install ydiff

To install on FreeBSD:

pkg install ydiff

Type ydiff -h to show usage:

$ ydiff -h
Usage: ydiff [options] [file|dir ...]

View colored, incremental diff in a workspace or from stdin, with side by side
and auto pager support

Options:
  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -s, --side-by-side    enable side-by-side mode (default True; DEPRECATED)
  -u, --unified         show diff in unified mode (disables side-by-side mode)
  -w N, --width=N       set text width for side-by-side mode, 0 (default) for
                        auto detection and fallback to 80 when not possible
  -l, --log             show log with changes from revision control
  -c WHEN, --color=WHEN
                        colorize mode 'auto' (default), 'always', or 'never'
  -t N, --tab-width=N   convert tab chars to this many spaces (default: 8)
  --wrap                wrap long lines in side-by-side mode (default True;
                        DEPRECATED)
  --nowrap, --no-wrap   do not wrap long lines in side-by-side mode
  -p PAGER, --pager=PAGER
                        pager application to feed output to, default is 'less'
  -o OPT, --pager-options=OPT
                        options to supply to pager application
  --theme=THEME         option to pick a color theme (one of default, dark,
                        light)

  Note:
    Option parser will stop on first unknown option and pass them down to
    underneath revision control. Environment variable YDIFF_OPTIONS may be
    used to specify default options that will be placed at the beginning
    of the argument list.

Read diff from local modification in a Git/Mercurial/Perforce/Svn workspace (output from e.g. git diff, svn diff):

cd proj-workspace
ydiff                       # view colored side by side diff, auto set text
                            # width based on terminal size
ydiff -u                    # view colored incremental diff in unified mode
ydiff -w 90                 # use text width 90, wrap long lines
ydiff --no-wrap             # auto set text width but do not wrap long lines
ydiff file1 dir2            # view modification of given files/dirs only
ydiff -w90 -- -U10          # pass '-U10' to underneath revision diff tool
ydiff -w90 -U10             # '--' is optional as it's unknown to ydiff
ydiff --cached              # show git staged diff (git diff --cached)
ydiff -r1234                # show svn diff to revision 1234

Read log with changes in a Git/Mercurial/Svn workspace (output from e.g. git log -p, svn log --diff), note --diff option is new in svn 1.7.0:

cd proj-workspace
ydiff -l                    # read log along with changes, side by side
ydiff -lu                   # equivalent to ydiff -l -u, unified mode
ydiff -l -w90 --no-wrap     # set text width 90 and disable wrapping
ydiff -l file1 dir2         # see log with changes of given files/dirs only

Utilize a specific pager application:

ydiff -p more                   # use "more" as a pager
ydiff -p cat                    # when neither less nor more is avilable
ydiff -o "-FRSX --shift 2"      # custmized option (pager defaults to less)

Pipe in a diff:

git log -p -2 | ydiff       # view git log with changes of last 2 commits
git show 15bfa | ydiff      # view a given git commit, side by side
svn diff -r1234 | ydiff     # view svn diff comparing to given revision
diff -u file1 file2 | ydiff # view diff between two files (note the '-u')
diff -ur dir1 dir2 | ydiff  # view diff between two dirs

# View diff in a GitHub pull request, side by side
curl https://github.com/ymattw/ydiff/pull/11.diff | ydiff

# View a patch file in colored unified format.
ydiff -u < foo.patch

Redirect output to another patch file is safe even without -u:

svn diff -r PREV | ydiff > my.patch

1. Ydiff only supports diffs in Unified Format. Diffs in other format may be converted to Unified Format via tool filterdiff (usually offered by package patchutils.)

2. Environment variable YDIFF_OPTIONS may be used to specify default options that will be placed at the beginning of the argument list, for example:

   export YDIFF_OPTIONS='-w100'
   ydiff foo  # equivalent to "ydiff -w100 foo"

3. If you feel more comfortable with a command such as git d to trigger the ydiff command, you may symlink the executable to one named git-d, or configure an alias:

   # Create a symlink git-d -> ydiff
   D=$(dirname $(which ydiff)); ln -s ydiff $D/git-d
   
   # Or configure an alias
   git config --global alias.d '!ydiff'

• Wide characters may cause alignment problem in side-by-side mode.
• Terminal might be in a mess on exception (type reset can fix it).