CODE EXAMPLE FOR SHELL

add kdiff3 to git

# configure your windows envrionment 
# download from https://download.kde.org/stable/kdiff3/

git config --global merge.tool kdiff3
git config --global mergetool.kdiff3.path "C:/Program Files/KDiff3/bin/kdiff3.exe"
git config --global mergetool.kdiff3.trustExitCode false

git config --global diff.guitool kdiff3
git config --global difftool.kdiff3.path "C:/Program Files/KDiff3/bin/kdiff3.exe"
git config --global difftool.kdiff3.trustExitCode false

# configure ubuntu
sudo apt install kdiff3

git config --global merge.tool kdiff3
git config --global mergetool.kdiff3.path "/usr/bin/kdiff3"
git config --global mergetool.kdiff3.trustExitCode false

git config --global diff.guitool kdiff3
git config --global difftool.kdiff3.path "/user/bin/kdiff3"
git config --global difftool.kdiff3.trustExitCode false

# to invoke merge run
git mergetool --tool=kdiff3