sharness.d: add support for heredoc test bodies

problem: quoting is annoying, and having to escape quotes in every
single test much moreso

solution: add *_hd versions of each of the test functions that accept
their code body on stdin (captured by cat) such that a heredoc, or even
a pipe if that's desirable for some reason, can provide the code.
Combined with a single-quoted heredoc and tab stripping (<<-'EOT' for
example) quoting woes disappear.  Vim syntax highlighting still WIP.

Author: trws

t/sharness.d/heredoc.sh

@@ -0,0 +1,24 @@
+test_expect_success_hd() {
+	test "$#" = 2 && { test_prereq=$1; shift; } || test_prereq=
+	local TEST_CODE
+	# these extra newlines are intentional, and mimic the ones we get
+	# naturally in the non-heredoc case
+	TEST_CODE="\
+
+	$(cat)
+	"
+	test_expect_success "$test_prereq" "'$1'" "$TEST_CODE"
+}
+
+test_expect_failure_hd() {
+	test "$#" = 2 && { test_prereq=$1; shift; } || test_prereq=
+	local TEST_CODE
+	# these extra newlines are intentional, and mimic the ones we get
+	# naturally in the non-heredoc case
+	TEST_CODE="\
+
+	$(cat)
+	"
+	test_expect_failure "$test_prereq" "'$1'" "$TEST_CODE"
+}
+

t/t0001-basic.t

@@ -24,6 +24,18 @@ path_printenv=$(which printenv)
 test_expect_success 'TEST_NAME is set' '
 	test -n "$TEST_NAME"
 '
+test_expect_success_hd 'heredoc tests work: success' <<-'EOT'
+	test -n "$TEST_NAME" &&
+	# embedded heredoc
+	cat >tmp.sh <<-EOF &&
+	true
+	EOF
+	chmod +x tmp.sh &&
+	./tmp.sh
+EOT
+test_expect_failure_hd 'heredoc tests work: failure' <<'EOT'
+	test -n ""
+EOT
 test_expect_success 'run_timeout works' '
 	test_expect_code 142 run_timeout -s ALRM 0.001 sleep 2
 '