tests: fix broken &&-chains in {...} groups

The top-level &&-chain checker built into t/test-lib.sh causes tests to
magically exit with code 117 if the &&-chain is broken. However, it has
the shortcoming that the magic does not work within `{...}` groups,
`(...)` subshells, `$(...)` substitutions, or within bodies of compound
statements, such as `if`, `for`, `while`, `case`, etc. `chainlint.sed`
partly fills in the gap by catching broken &&-chains in `(...)`
subshells, but bugs can still lurk behind broken &&-chains in the other
cases.

Fix broken &&-chains in `{...}` groups in order to reduce the number of
possible lurking bugs.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5515-fetch-merge-logic.sh

@@ -191,17 +191,17 @@ do
 		cp "$expect_r" expect_r &&
 		convert_expected expect_r sed_script &&
 		{
-			echo "# $cmd"
-			set x $cmd; shift
-			git symbolic-ref HEAD refs/heads/$1 ; shift
-			rm -f .git/FETCH_HEAD
+			echo "# $cmd" &&
+			set x $cmd && shift &&
+			git symbolic-ref HEAD refs/heads/$1 && shift &&
+			rm -f .git/FETCH_HEAD &&
 			git for-each-ref \
 				refs/heads refs/remotes/rem refs/tags |
 			while read val type refname
 			do
 				git update-ref -d "$refname" "$val"
-			done
-			git fetch "$@" >/dev/null
+			done &&
+			git fetch "$@" >/dev/null &&
 			cat .git/FETCH_HEAD
 		} >"$actual_f" &&
 		git show-ref >"$actual_r" &&