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

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:

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

ymattw's answer is also pretty neat, using ydiff

See also:

https://git-scm.com/book/en/v2/Customizing-Git-Git-Configuration
git diff --help
http://www.pixelbeat.org/programming/diffs/

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)

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
```
Using git config

use "git config" to define where your wrapper script can be found:
```
 git config --global diff.external ~/scripts/my_diff.sh
```
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