Using the below configuration,
[diff]
tool = vimdiff
[difftool]
[difftool "vimdiff"]
cmd = "$EDITOR -d \"$LOCAL\" \"$REMOTE\"; sleep 1"
and using "git diff" during a merge conflict (I specifically don't use "git merge" here), not the specified difftool (vimdiff), but the built-in diff is used (which gives me a patch-like display). When using "git diff" (the very same command) when not in a merge conflict, "vimdiff" is used as expected.
Is this behavior built-in, and can it be overridden?