Merge branch 'maint'

* maint:
  tests: avoid one last `...` command substitution in 'test-init.sh'
  maintcheck: guard against `...` for command substitution in test cases
  tests: more uses of $(...) over `...` for command substitution
  cosmetics: quote `like this', not 'like this', in a couple of tests
  readme: clarify/extend few entries in 't/README'
  readme: better separation of entries in 't/README'
  readme: subsections "Do" and "Do not" in 't/README' merged
  tests: new requirement 'grep-nonprint'
  cosmetics: fix description of an expected error message in a test
  tests: assume automake quotes 'like this', not `like this'

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

diff --cc syntax-checks.mk
index d9302da,417ae5e..77d2f42
--- 1/syntax-checks.mk
--- 2/syntax-checks.mk
+++ b/syntax-checks.mk
@@@ -55,9 -56,9 +55,10 @@@ sc_perl_at_uscore_in_scalar_context 
  sc_perl_local \
  sc_AMDEP_TRUE_in_automake_in \
  sc_tests_make_without_am_makeflags \
 +$(sc_obsolete_requirements_rules) \
  sc_tests_obsolete_variables \
  sc_tests_here_document_format \
+ sc_tests_command_subst \
  sc_tests_Exit_not_exit \
  sc_tests_automake_fails \
  sc_tests_required_after_defs \

diff --cc t/ax/tap-summary-aux.sh
Simple merge

diff --cc t/ax/test-init.sh
Simple merge

diff --cc t/parallel-tests-no-color-in-log.sh
Simple merge

diff --cc t/parallel-tests-reset-term.sh
index 4cd8086,9335d61..52e15c0
--- 1/t/parallel-tests-reset-term.sh
--- 2/t/parallel-tests-reset-term.sh
+++ b/t/parallel-tests-reset-term.sh
@@@ -14,23 -14,14 +14,14 @@@
  # You should have received a copy of the GNU General Public License
  # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  
 -# Check that the parallel-tests driver correctly handle overrides of the
 +# Check that the testsuite harness correctly handle overrides of the
  # TERM variable by either TESTS_ENVIRONMENT and AM_TESTS_ENVIRONMENT.
  
+ required='grep-nonprint'
  . ./defs || Exit 1
  
- esc='\e['
- 
  TERM=ansi; export TERM
  
- # Check that grep can parse nonprinting characters.
- # BSD 'grep' works from a pipe, but not a seekable file.
- # GNU or BSD 'grep -a' works on files, but is not portable.
- case `echo "$esc" | $FGREP "$esc"` in
-   "$esc") ;;
-   *) skip_ "$FGREP can't parse nonprinting characters" ;;
- esac
- 
  cat >> configure.ac << 'END'
  AC_OUTPUT
  END

diff --cc t/vtexi4.sh
index ee9d078,dcdcf85..975bf0e
--- 1/t/vtexi4.sh
--- 2/t/vtexi4.sh
+++ b/t/vtexi4.sh
@@@ -21,7 -21,7 +21,7 @@@
  # for more vers*.texi files, and does not require makeinfo, tex and
  # texi2dvi.
  
- required='makeinfo tex texi2dvi'
 -required='makeinfo tex texi2dvi-o grep-nonprint'
++required='makeinfo tex texi2dvi grep-nonprint'
  . ./defs || Exit 1
  
  test $(LC_ALL=C date '+%u') -gt 0 && test $(LC_ALL=C date '+%u') -lt 8 \