Adding only a portion of a file

See https://git-extensions-documentation.readthedocs.io/en/latest/commit.html#staging-selected-lines

In the commit dialog, we do not have to commit all of the changes of a file. In the diff view on the right, we can select individual lines for the next commit, and press the [S] key or the Stage context menu item to add the lines to the staging area.

You may want to turn the ignore white space options off which can be located at the dock bar on the right top of the diff view when the view is focused.

Command line:

git add -i
# or
git add --interactive