patch-id: fix antipatterns in tests

Clean up the tests for patch-id by moving file preparation
tasks inside the test body and redirecting files directly into
stdin instead of using 'cat'.

Signed-off-by: Jerry Zhang <jerry@skydio.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4204-patch-id.sh

@@ -166,40 +166,38 @@ test_expect_success 'patch-id respects config from subdir' '
 	)
 '
 
-cat >nonl <<\EOF
-diff --git i/a w/a
-index e69de29..2e65efe 100644
---- i/a
-+++ w/a
-@@ -0,0 +1 @@
-+a
-\ No newline at end of file
-diff --git i/b w/b
-index e69de29..6178079 100644
---- i/b
-+++ w/b
-@@ -0,0 +1 @@
-+b
-EOF
-
-cat >withnl <<\EOF
-diff --git i/a w/a
-index e69de29..7898192 100644
---- i/a
-+++ w/a
-@@ -0,0 +1 @@
-+a
-diff --git i/b w/b
-index e69de29..6178079 100644
---- i/b
-+++ w/b
-@@ -0,0 +1 @@
-+b
-EOF
-
 test_expect_success 'patch-id handles no-nl-at-eof markers' '
-	cat nonl | calc_patch_id nonl &&
-	cat withnl | calc_patch_id withnl &&
+	cat >nonl <<-\EOF &&
+	diff --git i/a w/a
+	index e69de29..2e65efe 100644
+	--- i/a
+	+++ w/a
+	@@ -0,0 +1 @@
+	+a
+	\ No newline at end of file
+	diff --git i/b w/b
+	index e69de29..6178079 100644
+	--- i/b
+	+++ w/b
+	@@ -0,0 +1 @@
+	+b
+	EOF
+	cat >withnl <<-\EOF &&
+	diff --git i/a w/a
+	index e69de29..7898192 100644
+	--- i/a
+	+++ w/a
+	@@ -0,0 +1 @@
+	+a
+	diff --git i/b w/b
+	index e69de29..6178079 100644
+	--- i/b
+	+++ w/b
+	@@ -0,0 +1 @@
+	+b
+	EOF
+	calc_patch_id nonl <nonl &&
+	calc_patch_id withnl <withnl &&
 	test_cmp patch-id_nonl patch-id_withnl
 '
 test_done