Merge branch 'sg/trace2-rename'

Dev support update to help tracing out tests.

* sg/trace2-rename:
  trace2: correct typo in technical documentation
  Revert "test-lib: whitelist GIT_TR2_* in the environment"

diff --combined t/test-lib.sh
index 4b346467df7aaf2e5215f7ebb3bfb4ae13a3ffbc,57f7c30377faa9867c7651a2b1ec16f2351bc000..d1ba33745a24c92411baca54604c853373b9bc39
--- 1/t/test-lib.sh
--- 2/t/test-lib.sh
+++ b/t/test-lib.sh
@@@ -386,7 -386,6 +386,6 @@@ unset VISUAL EMAIL LANGUAGE COLUMNS $("
        my @env = keys %ENV;
        my $ok = join("|", qw(
                TRACE
-               TR2_
                DEBUG
                TEST
                .*_TEST
@@@ -1607,7 -1606,3 +1606,7 @@@ test_lazy_prereq SHA1 
  test_lazy_prereq REBASE_P '
        test -z "$GIT_TEST_SKIP_REBASE_P"
  '
 +
 +test_lazy_prereq FAIL_PREREQS '
 +      test -n "$GIT_TEST_FAIL_PREREQS"
 +'