implied by other options like --valgrind and
GIT_TEST_INSTALLED.
+--root=<directory>::
+ Create "trash" directories used to store all temporary data during
+ testing under <directory>, instead of the t/ directory.
+ Using this option with a RAM-based filesystem (such as tmpfs)
+ can massively speed up the test suite.
+
You can also set the GIT_TEST_INSTALLED environment variable to
the bindir of an existing git installation to test that installation.
You still need to have built this git sandbox, from which various