How to improve git's diff highlighting?

Question

The output of git diff is optimized for code which tends to be one statement per line whereas text can (if authors like me are too lazy to use line breaks) cause diff output which is very hard to read and more of a "Where's Wally?" search than reading diff output

whereas highlighting as done on GitLab's or GitHub's web frontend shows the difference immediately

I'm aware that I'm comparing HTML and plain text (apples and oranges), however it should be possible to improve the git diff output by using different colors or adding marker characters around a change (JUnit uses [] around insertions which isn't great to read, but an example for what I mean) and it would be the first time that there's something I expect to be somewhere available in git that actually was not.

Answer 1

You could use the --word-diff[=<mode>] option to make it easier to see which words have changed within a line. This is described in the man page as

Show a word diff, using the <mode> to delimit changed words. By default, words are delimited by whitespace; see --word-diff-regex below. The <mode> defaults to plain, and must be one of:

• color – Highlight changed words using only colors. Implies --color.

• plain – Show words as [-removed-] and {+added+}. Makes no attempts to escape the delimiters if they appear in the input, so the output may be ambiguous.

• porcelain – Use a special line-based format intended for script consumption. Added/removed/unchanged runs are printed in the usual unified diff format, starting with a +/-/` ` character at the beginning of the line and extending to the end of the line. Newlines in the input are represented by a tilde ~ on a line of its own.

• none – Disable word diff again.

Note that despite the name of the first mode, color is used to highlight the changed parts in all modes if enabled.

Answer 2

The word-diff suggested in the other answer isn't exactly what gitlab/github do. To get same effect, you can use diff-highlight script that is distributed with git.

1. First find path to diff-highlight script. It varies between systems, and is not usually in $PATH. You can find it with your package manager, for example:

   1. Fedora: rpm -ql git | grep diff-highlight
   2. Debian/Ubuntu/Mint: dpkg -L git | grep diff-highlight
   3. Archlinux: pacman -Ql git | grep diff-highlight

2. Now, execute the following two commands, which will add to your ~/.gitconfig the necessary settings:

   $ git config --global core.pager 'perl /usr/share/git/diff-highlight/diff-highlight | less'
   $ git config --global interactive.difffilter 'perl /usr/share/git/diff-highlight/diff-highlight'
   

   I'm using perl here instead of calling the script directly because some distros, it seems, do not set executable bit on the script. IMO this is a package bug which should be reported. Anyway, this answer should work regardless.

Now log, diff, show commands should show difference word-by-word. Screenshot:

Answer 3

Also worth mentioning is diffr. It's written in Rust and uses Myers longest common subsequence algorithm. Compared to git's diff-highlight it gives better results, see:

git's diff-highlight:

diffr:

Once installed, making use of it is similar to that of diff-highlight, so for example execute these two commands to add diffr to your global config:

$ git config --global core.pager 'diffr | less'
$ git config --global interactive.difffilter diffr

Answer 4

Delta is a modern alternative to the postprocessing tools in other answers.

It is highly configurable (with emulation modes for diff-highlight and diff-so-fancy) and includes many features not found in other tools: side-by-side views, syntax highlighting, and coloring of merge conflicts and git blame output.

The Delta documentation also has an overview of related projects that mentions a few more ad-hoc tools that can produce similar output.

Answer 5

Sometimes just changing the coloring engine of git helps so much. Try diff-so-fancy.

Answer 6

To expand on @Hi-Angel answer, we could use a wrapper script to find the diff-highlight contrib script and place it in $PATH. Then use the wrapper script in your .gitconfig.

The script will try to find contrib/diff-highlight. We will name the script wrapper diff-highlight and place it in $PATH:

#!/bin/sh
# diff-highlight locates the diff-highlight script in the git source tree and
# runs it.
# https://github.com/git/git/blob/master/contrib/diff-highlight

hilite=

for prefix in /usr/share /usr/local/share; do
    # First try git-core directory
    if [ -f "$prefix/git-core/contrib/diff-highlight" ]; then
        hilite="/usr/share/git-core/contrib/diff-highlight"
    elif [ -d "$prefix/git-core/contrib/diff-highlight" ]; then
        hilite="$prefix/git-core/contrib/diff-highlight/diff-highlight"
        # Then try git contrib directory
    elif [ -f "$prefix/git/contrib/diff-highlight" ]; then
        hilite="$prefix/git/contrib/diff-highlight"
    elif [ -d "$prefix/git/contrib/diff-highlight" ]; then
        hilite="$prefix/git/contrib/diff-highlight/diff-highlight"
        # Try git directory
    elif [ -f "$prefix/git/diff-highlight" ]; then
        hilite="$prefix/git/diff-highlight"
    elif [ -d "$prefix/git/diff-highlight" ]; then
        hilite="$prefix/git/diff-highlight/diff-highlight"
        # Then try doc directory
    elif [ -f "$prefix/doc/git/contrib/diff-highlight" ]; then
        hilite="$prefix/doc/git/contrib/diff-highlight"
    elif [ -d "$prefix/doc/git/contrib/diff-highlight" ]; then
        hilite="$prefix/doc/git/contrib/diff-highlight/diff-highlight"
    fi
    if [ -n "$hilite" ]; then
        break
    fi
done

if [ -x "$hilite" ]; then
    exec "$hilite" "$@"
elif command -v perl >/dev/null 2>&1; then
    perl "$hilite" "$@"
else
    cat
fi

You can also find this script in my dotfiles.

Then change the git pager to use the wrapper script:

$ git config --global core.pager 'diff-highlight | less'
$ git config --global interactive.diffFilter 'diff-highlight'

Answer 7

Another option (in Rust): Wilfred/difftastic

Difftastic is a structural diff tool that compares files based on their syntax.

See Git usage:

One-Off Usage

You can use GIT_EXTERNAL_DIFF for a one-off git command.

View uncommitted changes with difftastic:

$ GIT_EXTERNAL_DIFF=difft git diff

View changes from the most recent commit with difftastic:

$ GIT_EXTERNAL_DIFF=difft git show HEAD --ext-diff

View changes from recent commits on the current branch with difftastic:

$ GIT_EXTERNAL_DIFF=difft git log -p --ext-diff

Regular Usage

If you like difftastic, we recommend that you configure git aliases so you can use difftastic more easily.

Add the following to your ~/.gitconfig to use difftastic as a difftool.

[diff]
        tool = difftastic

[difftool]
        prompt = false

[difftool "difftastic"]
        cmd = difft "$LOCAL" "$REMOTE"

[pager]
        difftool = true

You can now use the following command to see changes with difftastic, equivalent to git diff:

$ git difftool

We recommend that you set up a shorter alias for this command in your ~/.gitconfig:

# `git dft` is less to type than `git difftool`.
[alias]
        dft = difftool

For other commands, we also recommend that you set up aliases that are equivalent to the one-off commands shown above.

# `git dlog` to show `git log -p` with difftastic.
[alias]
        dlog = "!f() { GIT_EXTERNAL_DIFF=difft git log -p --ext-diff $@; }; f"

Difftastic By Default

If you want to use difftastic as your default diff tool, add the following to your ~/.gitconfig.

[diff]
    external = difft

This only applies to git diff. For other git commands, you still need to specify --ext-diff, or use an alias as described above.

$ git diff
$ git show HEAD --ext-diff
$ git log -p --ext-diff