I have found it, the line is called hunk header and the documentation says how to customize it:
Defining a custom hunk-header
Each group of changes (called a "hunk") in the textual diff output is prefixed with a line of the form:
@@ -k,l +n,m @@ TEXT
This is called a hunk header. The "TEXT" portion is by default a line that begins with an alphabet, an underscore or a dollar sign; this matches what GNU diff -p
output uses. This default selection however is not suited for some contents, and you can use a customized pattern to make a selection.
First, in .gitattributes, you would assign the diff
attribute for paths.
*.tex diff=tex
Then, you would define a "diff.tex.xfuncname" configuration to specify a regular expression that matches a line that you would want to appear as the hunk header "TEXT". Add a section to your $GIT_DIR/config
file (or $HOME/.gitconfig
file) like this:
[diff "tex"]
xfuncname = "^(\\\\(sub)*section\\{.*)$"
Note. A single level of backslashes are eaten by the configuration file parser, so you would need to double the backslashes; the pattern above picks a line that begins with a backslash, and zero or more occurrences of sub followed by section followed by open brace, to the end of line.