Merge branch 'es/chain-lint-in-subshell'

Look for broken "&&" chains that are hidden in subshell, many of which have been found and corrected. * es/chain-lint-in-subshell: t/chainlint.sed: drop extra spaces from regex character class t/chainlint: add chainlint "specialized" test cases t/chainlint: add chainlint "complex" test cases t/chainlint: add chainlint "cuddled" test cases t/chainlint: add chainlint "loop" and "conditional" test cases t/chainlint: add chainlint "nested subshell" test cases t/chainlint: add chainlint "one-liner" test cases t/chainlint: add chainlint "whitespace" test cases t/chainlint: add chainlint "basic" test cases t/Makefile: add machinery to check correctness of chainlint.sed t/test-lib: teach --chain-lint to detect broken &&-chains in subshells