t7600: clean up style

Clean up the 'merge --squash c3 with c7' test by removing some
unnecessary braces and removing a pipe.

Also, generally cleanup style by unindenting a here-doc, removing stray
spaces after a redirection operator and allowing sed to open its own
input instead of redirecting input from the shell.

Helped-by: SZEDER Gábor <szeder.dev@gmail.com>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Denton-L

t/t7600-merge.sh

@@ -233,17 +233,16 @@ test_expect_success 'merge --squash c3 with c7' '
 	cat result.9z >file &&
 	git commit --no-edit -a &&
 
-	{
-		cat <<-EOF
-		Squashed commit of the following:
+	cat >expect <<-EOF &&
+	Squashed commit of the following:
 
-		$(git show -s c7)
+	$(git show -s c7)
 
-		# Conflicts:
-		#	file
-		EOF
-	} >expect &&
-	git cat-file commit HEAD | sed -e '1,/^$/d' >actual &&
+	# Conflicts:
+	#	file
+	EOF
+	git cat-file commit HEAD >raw &&
+	sed -e '1,/^$/d' raw >actual &&
 	test_cmp expect actual
 '
 
@@ -680,10 +679,10 @@ cat >editor <<\EOF
 (
 	echo "Merge work done on the side branch c1"
 	echo
-	cat <"$1"
+	cat "$1"
 ) >"$1.tmp" && mv "$1.tmp" "$1"
 # strip comments and blank lines from end of message
-sed -e '/^#/d' < "$1" | sed -e :a -e '/^\n*$/{$d;N;ba' -e '}' > expected
+sed -e '/^#/d' "$1" | sed -e :a -e '/^\n*$/{$d;N;ba' -e '}' >expected
 EOF
 chmod 755 editor
 
@@ -768,14 +767,14 @@ test_expect_success 'set up mod-256 conflict scenario' '
 	git commit -m base &&
 
 	# one side changes the first line of each to "master"
-	sed s/-1/-master/ <file >tmp &&
+	sed s/-1/-master/ file >tmp &&
 	mv tmp file &&
 	git commit -am master &&
 
 	# and the other to "side"; merging the two will
 	# yield 256 separate conflicts
 	git checkout -b side HEAD^ &&
-	sed s/-1/-side/ <file >tmp &&
+	sed s/-1/-side/ file >tmp &&
 	mv tmp file &&
 	git commit -am side
 '
@@ -814,7 +813,7 @@ EOF
 test_expect_success EXECKEEPSPID 'killed merge can be completed with --continue' '
 	git reset --hard c0 &&
 	! "$SHELL_PATH" -c '\''
-	  echo kill -TERM $$ >> .git/FAKE_EDITOR
+	  echo kill -TERM $$ >>.git/FAKE_EDITOR
 	  GIT_EDITOR=.git/FAKE_EDITOR
 	  export GIT_EDITOR
 	  exec git merge --no-ff --edit c1'\'' &&