-working directory and HEAD. Later this tool can be improved upon to use the
-tool listed in the config file (difftool), or if none present fall back to
-a 'normal' git diff.
+working directory and HEAD. If in the git config diff.tool is set, this
+program is passed the name of the two temporary directories containing the
+changed files of each revision. If diff.tool is not defined, the fall-back
+is to diff.