Tests: optionally skip redirecting stdin/stdout/stderr

There is a really useful debugging technique developed by Sverre
Rabbelier that inserts "bash &&" somewhere in the test scripts, letting
the developer interact at given points with the current state.

Another debugging technique, used a lot by this here coder, is to run
certain executables via gdb by guarding a "gdb -args" call in
bin-wrappers/git.

Both techniques were disabled by 781f76b(test-lib: redirect stdin of
tests).

Let's reinstate the ability to run an interactive shell by making the
redirection optional: setting the TEST_NO_REDIRECT environment variable
will skip the redirection.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

t/test-lib.sh

@@ -17,6 +17,7 @@
 
 # for git on windows so stdin will not be misdetected as attached to a
 # terminal
+test -z "$TEST_NO_REDIRECT" ||
 exec < /dev/null
 
 # Keep the original TERM for say_color
@@ -511,7 +512,12 @@ test_eval_ () {
 	# The test itself is run with stderr put back to &4 (so either to
 	# /dev/null, or to the original stderr if --verbose was used).
 	{
-		test_eval_inner_ "$@" </dev/null >&3 2>&4
+		if test -z "$TEST_NO_REDIRECT"
+		then
+			test_eval_inner_ "$@" </dev/null >&3 2>&4
+		else
+			test_eval_inner_ "$@"
+		fi
 		test_eval_ret_=$?
 		if test "$trace" = t
 		then