A collection of additional "custom hunk header" patterns for .gitattributes. This provides better context in the diff hunk header.

attributes

*.tex   diff=tex
*.bib   diff=bibtex
*.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=matlab
*.py    diff=python
*.rb    diff=ruby
*.php   diff=php
*.pl    diff=perl
*.html  diff=html
*.xhtml diff=html
*.f     diff=fortran

*.lisp  diff=lisp
*.el    diff=lisp
*.r     diff=rstats
*.texi* diff=texinfo
*.org   diff=orgmode
*.rs    diff=rust

*.pdf   diff=pdf
*.png   diff=exif
*.jpg   diff=exif
*.jpeg  diff=exif
*.gif   diff=exif

config

[diff "lisp"]
      xfuncname = "^(\\(.*)$"
#      xfuncname = "^(\\((cl-)?def(un|macro|method).*)$"
[diff "rstats"]
      xfuncname = "^([a-zA-z.]+ <- function.*)$"
[diff "texinfo"]
# from http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=blob;f=.gitattributes;h=c3b2926c78c939d94358cc63d051a70d38cfea5d;hb=HEAD
      xfuncname = "^@node[ \t][ \t]*\\([^,][^,]*\\)"
[diff "orgmode"]
      xfuncname = "^(\\*+.*)$"
#[diff "css"]
#      xfuncname = "^([a-zA-Z#.@][^\\}]*)$"
#      xfuncname = "^(.*\\{)$"
[diff "rust"] # Thanks to csabahenk
      xfuncname = "^[ \t]*(pub|)[ \t]*((fn|struct|enum|impl|trait|mod)[^;]*)$"
[diff "exif"]
      binary = true
# sudo apt-get install libimage-exiftool-perl
      textconv = exiftool
[diff "pdf"]
      textconv = pdftotext-stdout
# sudo apt-get install pdftotext
# copy the following to a script pdftotext-stdout somehwere in $PATH
#  #!/bin/bash
#  pdftotext "$@" -

See gitattributes(5) for more information.

Add the stuff in attributes to your ${XDG_CONFIG_HOME:-~/.config}/git/attributes and the stuff in config to your ${XDG_CONFIG_HOME:-~/.config}/git/config (or ~/.gitconfig)

Suggested improvement:

[diff "rust"]
      xfuncname = "^[ \t]*(pub|)[ \t]*((fn|struct|enum|impl|trait|mod)[^;]*)$"

Emacs' git-modes comes with several modes for git including gitattributes-mode and gitconfig-mode for editing git attributes and config files.

http://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=lib/git-merge-changelog.c

for dealing with ChangeLog merges in git (and hg)

For javascript:

[diff "ecmascript"]
        xfuncname = "^((.*function.*)|([ \t]+it\\(.*))$"

Is there c++ xfuncname ?

Further set up for diffing binary documents.

I am searching for patterns for haskell or nix. Can anyone help?

The built-in filter for php did not work well for me.
This works better.

[diff "php"]
        xfuncname = "^.*(\\b(((public|protected|private|static)\\s+){1,4}function\\s+[_A-Za-z][_A-Za-z0-9]+\\b\\s*\\()).*$"

Sadly I have minified files on some repos, and the only interesting stuff there is the size:

# .gitattributes
*.min.*       diff=minified

[diff "minified"]
        textconv = size

#!/bin/bash

file=$1

bits=$(du -b "$file" | cut -f1)
size=$(du -h "$file" | cut -f1)
compressed_size=$( < "$file" gzip | wc -c - | cut -d' ' -f 1 | numfmt --to=iec )

printf "%10sb -> %5s (%4s gziped)\n" "$bits" "$size" "$compressed_size"

Outputs something like:

diff --git c/assets/app.min.js w/assets/app.min.js
index 0c9178d..077b550 100644
--- c/assets/app.min.js
+++ w/assets/app.min.js
@@ -1 +1 @@
-     41907b ->   44K ( 11K gziped)
+     43031b ->   44K ( 12K gziped)

As of git 2.50, there is now built-in patterns for *ini config files.
Also missing from this list is java and rust (built in now).
See the source for all supported patterns:
https://github.com/git/git/blob/master/userdiff.c