Hi Jaakko, On Tue, 6 Sep 2016, Jaakko Pääkkönen wrote: > I am using beyond compare, but it does not really matter which one > because even I create a dummy script as a external diff program, it > will not get called ever. Only internal diff is started. Any chance you can come up with an MCVE [*1*] using a dummy script? > > Re-installing git will not remove the problem. I am using the latest git > > Any hints how I can debug git difftool? Sure. First hint: set GIT_TRACE=1. Next hint: difftool is a shell script, so you can modify it, say, by inserting a `set -x` which will trace the commands that are called. Ciao, Johannes Footnote *1*: http://stackoverflow.com/help/mcve