Git: How configure KDiff3 as merge tool and diff tool

These sites were very helpful, almost, mergetool and difftool. I used the global configuration, but can be used by repository without problems. You just need to execute the following commands:

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

Note that the latest version kdiff3 moved the executable from the root of the application folder C:/Program Files/KDiff3 into the bin/ folder inside the application folder. If you're using an older version, remove "bin/" from the paths above.

The use of the trustExitCode option depends on what you want to do when diff tool returns. From documentation:

git-difftool invokes a diff tool individually on each file. Errors reported by the diff tool are ignored by default. Use --trust-exit-code to make git-difftool exit when an invoked diff tool returns a non-zero exit code.

Just to extend the @Joseph's answer:

After applying these commands your global .gitconfig file will have the following lines (to speed up the process you can just copy them in the file):

[merge]
    tool = kdiff3
[mergetool "kdiff3"]
    path = C:/Program Files/KDiff3/kdiff3.exe
    trustExitCode = false
[diff]
    guitool = kdiff3
[difftool "kdiff3"]
    path = C:/Program Files/KDiff3/kdiff3.exe
    trustExitCode = false

For Mac users

Here is @Joseph's accepted answer, but with the default Mac install path location of kdiff3

(Note that you can copy and paste this and run it in one go)

git config --global --add merge.tool kdiff3 
git config --global --add mergetool.kdiff3.path  "/Applications/kdiff3.app/Contents/MacOS/kdiff3" 
git config --global --add mergetool.kdiff3.trustExitCode false

git config --global --add diff.guitool kdiff3
git config --global --add difftool.kdiff3.path "/Applications/kdiff3.app/Contents/MacOS/kdiff3"
git config --global --add difftool.kdiff3.trustExitCode false