On Sat, Nov 26, 2016 at 01:22:28PM +0100, Johannes Schindelin wrote: > In other words, GIT_CONFIG_PARAMETERS is *explicitly scrubbed* from the > environment when we run our tests (by the code block between the "before" > and the "after" statements in the diff above). Sorry if I wasn't clear. I meant to modify t7800 to run the tests twice, once with the existing script and once with the builtin. I.e., to set the variable after test-lib.sh has done its scrubbing, and then use a loop or similar to go through the tests twice. If you want to control it from outside the test script, you'd need something like: if test "$GIT_TEST_DIFFTOOL" = "builtin" then GIT_CONFIG_PARAMETERS=... fi -Peff