delta

To toggle features such as side-by-side on and off, you need to not turn on line-numbers or side-by-side etc in your main delta config (~/.gitconfig). Then, one approach is to use the [DELTA_FEATURES](../features-named-groups-of-settings.md) environment variable:

export DELTA_FEATURES=+side-by-side

and to undo that:

export DELTA_FEATURES=+

To make that convenient, you could use this shell function:

delta-toggle() {
    eval "export DELTA_FEATURES='$(-delta-features-toggle $1 | tee /dev/stderr)'"
}

where -delta-features-toggle is this Python script: https://github.com/dandavison/tools/blob/main/python/-delta-features-toggle.

Then

delta-toggle    # shows current features
delta-toggle s  # toggles side-by-side
delta-toggle l  # toggles line-numbers

(It might make sense to add something like this Python script to delta itself.)

Another approach is to use git aliases, e.g.

[alias]
    diff-side-by-side = -c delta.features=side-by-side diff