Search code examples
gitgit-diffcode-visualization

How can I get a side-by-side diff when I do "git diff"?

When I type git diff, I'd like to see a side-by-side diff, like with diff -y, or like to display the diff in an interactive diff tool like kdiff3. How can this be done?

Solution

  • Although Git has an internal implementation of diff, you can set up an external tool instead.

    There are two different ways to specify an external diff tool:

    1. setting the GIT_EXTERNAL_DIFF and the GIT_DIFF_OPTS environment variables.
    2. configuring the external diff tool via git config

    ymattw's answer is also pretty neat, using ydiff

    See also:

    When doing a git diff, Git checks both the settings of above environment variables and its .gitconfig file.

    By default, Git passes the following seven arguments to the diff program:

    path  old-file  old-hex old-mode  new-file  new-hex new-mode

    You typically only need the old-file and new-file parameters. Of course most diff tools only take two file names as an argument. This means that you need to write a small wrapper-script, which takes the arguments which Git provides to the script, and hands them on to the external git program of your choice.

    Let's say you put your wrapper-script under ~/scripts/my_diff.sh:

    #!/bin/bash
# un-comment one diff tool you'd like to use

# use standard diff command with options: (2023)
/usr/bin/diff -y "$2" "$5" 

# side-by-side diff with custom options:
# /usr/bin/sdiff -w200 -l "$2" "$5" 

# using kdiff3 as the side-by-side diff:
# /usr/bin/kdiff3 "$2" "$5"

# using Meld 
/usr/bin/meld "$2" "$5"

# using VIM
# /usr/bin/vim -d "$2" "$5"

    you then need to make that script executable:

    chmod a+x ~/scripts/my_diff.sh

    you then need to tell Git how and where to find your custom diff wrapper script. You have three choices how to do that: (I prefer editing the .gitconfig file)

    1. Using GIT_EXTERNAL_DIFF, GIT_DIFF_OPTS

      e.g. in your .bashrc or .bash_profile file you can set:

       GIT_EXTERNAL_DIFF=$HOME/scripts/my_diff.sh
 export GIT_EXTERNAL_DIFF

    2. Using git config

      use "git config" to define where your wrapper script can be found:

       git config --global diff.external ~/scripts/my_diff.sh

    3. Editing your ~/.gitconfig file

      you can edit your ~/.gitconfig file to add these lines:

       [diff]
   external = ~/scripts/my_diff.sh

    Note:

    Similarly to installing your custom diff tool, you can also install a custom merge-tool, which could be a visual merging tool to better help visualizing the merge. (see the progit.org page)

    See: http://fredpalma.com/518/visual-diff-and-merge-tool/ and https://git-scm.com/book/en/v2/Customizing-Git-Git-Configuration