An example .gitattributes file that will configure custom hunk header patterns for some common languages and file formats. See https://tekin.co.uk/2020/10/better-git-diff-output-for-ruby-python-elixir-and-more for more details.

.gitattributes

# Stick this in your home directory and point your Global Git config at it by running:
#
#  $ git config --global core.attributesfile ~/.gitattributes
#
# See https://tekin.co.uk/2020/10/better-git-diff-output-for-ruby-python-elixir-and-more for more details

*.c     diff=cpp
*.h     diff=cpp
*.c++   diff=cpp
*.h++   diff=cpp
*.cpp   diff=cpp
*.hpp   diff=cpp
*.cc    diff=cpp
*.hh    diff=cpp
*.m     diff=objc
*.mm    diff=objc
*.cs    diff=csharp
*.css   diff=css
*.html  diff=html
*.xhtml diff=html
*.ex    diff=elixir
*.exs   diff=elixir
*.go    diff=golang
*.php   diff=php
*.pl    diff=perl
*.py    diff=python
*.md    diff=markdown
*.rb    diff=ruby
*.rake  diff=ruby
*.rs    diff=rust
*.lisp  diff=lisp
*.el    diff=lisp

.gitconfig

# Additional manually-configured matchers you may want to add to your .gitconfig

[diff "rspec"]
        xfuncname = "^[ \t]*((RSpec|describe|context|it|before|after|around|feature|scenario|background)[ \t].*)$"
[diff "swift"]
    xfuncname = ^[ \t]*((class|func)[ \t].*)$

@dlinch there doesn't appear to be javascript support builtin. I only see java here: https://github.com/git/git/blob/master/userdiff.c#L78

Cheers @rickclare, updated now.

@dlinch yeah, as @DiegoSalazar points out, there is no pre-defined pattern for JavaScript built into Git. It is possible to define your own custom regular expression pattern though. See the docs on defining a custom hunk-header.

*.m diff=objc
*.mm diff=objc

This is awesome. Any thoughts on how you do this for an erb file ? should it be

*.erb diff=html

or

*.erb diff=erb

@Rafi993 There aren't any defined regex for ERb in the git source, so it's either HTML or nothing.

Thank you @citizen428

Edit:
I think you mentioned some other user by accident :)

This is great, thanks a lot! Super useful if you're using a less rich editor such as Vim and working mainly out of a terminal.

Thank you so much for this! I work with rspec and capybara a lot and found using the built-in ruby diff for spec files broke the hunk header entirely for them, so I wrote my own regex for specs based on the native ruby regex:

# .gitconfig

[diff "rspec"]
        xfuncname = "^[ \t]*((RSpec|describe|context|it|before|after|around|feature|scenario|background)[ \t].*)$"

You can then use "rspec" as a diff driver:

# .gitattributes

*.rb       diff=ruby
*_spec.rb  diff=rspec

@jimryan that’s super cool, thanks for sharing!

@jimryan Might want to add around too. Thanks!

@zubin Good point! I've updated the snippet above. Thanks!

Thank you for a great tip.
I found this gist as well and comment here for additional info.

https://gist.github.com/ruediger/5647207