pg_regress: Emit TAP compliant output

This converts pg_regress output format to emit TAP compliant output
while keeping it as human readable as possible for use without TAP
test harnesses. As verbose harness related information isn't really
supported by TAP this also reduces the verbosity of pg_regress runs
which makes scrolling through log output in buildfarm/CI runs a bit
easier as well.

As the meson TAP parser conumes whitespace, the leading indentation
for differentiating parallel tests from sequential tests has been
changed to a single character prefix.

This patch has been around for an extended period of time, reviewers
listed below may have been involved in reviewing a version quite
different from the version in this commit.  The original idea for
this patch was a hacking session with Jinbao Chen.

TAP format testing is also enabled in meson as of this.

Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Nikolay Shaplov <dhyan@nataraj.su>
Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Discussion: https://postgr.es/m/BD4B107D-7E53-4794-ACBA-275BEB4327C9@yesql.se
Discussion: https://postgr.es/m/20220221164736.rq3ornzjdkmwk2wo@alap3.anarazel.de

doc/src/sgml/regress.sgml

@@ -30,6 +30,8 @@
    parallel method starts up multiple server processes to run groups
    of tests in parallel.  Parallel testing adds confidence that
    interprocess communication and locking are working correctly.
+   Some tests may run sequentially even in the <quote>parallel</quote>
+   mode in case this is required by the test.
   </para>
 
   <sect2 id="regress-run-temp-inst">
@@ -43,12 +45,12 @@ make check
 </screen>
    in the top-level directory.  (Or you can change to
    <filename>src/test/regress</filename> and run the command there.)
+   Tests which are run in parallel are prefixed with <quote>+</quote>, and
+   tests which run sequentially are prefixed with <quote>-</quote>.
    At the end you should see something like:
 <screen>
 <computeroutput>
-=======================
- All 193 tests passed.
-=======================
+# All 213 tests passed.
 </computeroutput>
 </screen>
    or otherwise a note about which tests failed.  See <xref

meson.build

@@ -3118,6 +3118,7 @@ foreach test_dir : tests
       env.prepend('PATH', temp_install_bindir, test_dir['bd'])
 
       test_kwargs = {
+        'protocol': 'tap',
         'priority': 10,
         'timeout': 1000,
         'depends': test_deps + t.get('deps', []),

src/Makefile.global.in

@@ -444,7 +444,7 @@ ifeq ($(enable_tap_tests),yes)
 
 ifndef PGXS
 define prove_installcheck
-echo "+++ tap install-check in $(subdir) +++" && \
+echo "# +++ tap install-check in $(subdir) +++" && \
 rm -rf '$(CURDIR)'/tmp_check && \
 $(MKDIR_P) '$(CURDIR)'/tmp_check && \
 cd $(srcdir) && \
@@ -457,7 +457,7 @@ cd $(srcdir) && \
 endef
 else # PGXS case
 define prove_installcheck
-echo "+++ tap install-check in $(subdir) +++" && \
+echo "# +++ tap install-check in $(subdir) +++" && \
 rm -rf '$(CURDIR)'/tmp_check && \
 $(MKDIR_P) '$(CURDIR)'/tmp_check && \
 cd $(srcdir) && \
@@ -471,7 +471,7 @@ endef
 endif # PGXS
 
 define prove_check
-echo "+++ tap check in $(subdir) +++" && \
+echo "# +++ tap check in $(subdir) +++" && \
 rm -rf '$(CURDIR)'/tmp_check && \
 $(MKDIR_P) '$(CURDIR)'/tmp_check && \
 cd $(srcdir) && \
@@ -665,7 +665,7 @@ pg_regress_locale_flags = $(if $(ENCODING),--encoding=$(ENCODING)) $(NOLOCALE)
 pg_regress_clean_files = results/ regression.diffs regression.out tmp_check/ tmp_check_iso/ log/ output_iso/
 
 pg_regress_check = \
-    echo "+++ regress check in $(subdir) +++" && \
+    echo "\# +++ regress check in $(subdir) +++" && \
     $(with_temp_install) \
     $(top_builddir)/src/test/regress/pg_regress \
     --temp-instance=./tmp_check \
@@ -674,14 +674,14 @@ pg_regress_check = \
     $(TEMP_CONF) \
     $(pg_regress_locale_flags) $(EXTRA_REGRESS_OPTS)
 pg_regress_installcheck = \
-    echo "+++ regress install-check in $(subdir) +++" && \
+    echo "\# +++ regress install-check in $(subdir) +++" && \
     $(top_builddir)/src/test/regress/pg_regress \
     --inputdir=$(srcdir) \
     --bindir='$(bindir)' \
     $(pg_regress_locale_flags) $(EXTRA_REGRESS_OPTS)
 
 pg_isolation_regress_check = \
-    echo "+++ isolation check in $(subdir) +++" && \
+    echo "\# +++ isolation check in $(subdir) +++" && \
     $(with_temp_install) \
     $(top_builddir)/src/test/isolation/pg_isolation_regress \
     --temp-instance=./tmp_check_iso \
@@ -690,7 +690,7 @@ pg_isolation_regress_check = \
     $(TEMP_CONF) \
     $(pg_regress_locale_flags) $(EXTRA_REGRESS_OPTS)
 pg_isolation_regress_installcheck = \
-    echo "+++ isolation install-check in $(subdir) +++" && \
+    echo "\# +++ isolation install-check in $(subdir) +++" && \
     $(top_builddir)/src/test/isolation/pg_isolation_regress \
     --inputdir=$(srcdir) --outputdir=output_iso \
     --bindir='$(bindir)' \