Allow individual TAP tests to be run via PROVE_TESTS

Add a new optional Makefile variable PROVE_TESTS that, if passed as a
space-separated list of paths relative to the Makefile invoking
$(prove_check) or $(prove_installcheck), runs just those tests instead
of t/*.pl .

From: Craig Ringer <craig@2ndquadrant.com>
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>

src/Makefile.global.in

@@ -354,12 +354,12 @@ ifeq ($(enable_tap_tests),yes)
 
 define prove_installcheck
 rm -rf $(CURDIR)/tmp_check/log
-cd $(srcdir) && TESTDIR='$(CURDIR)' PATH="$(bindir):$$PATH" PGPORT='6$(DEF_PGPORT)' top_builddir='$(CURDIR)/$(top_builddir)' PG_REGRESS='$(CURDIR)/$(top_builddir)/src/test/regress/pg_regress' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) t/*.pl
+cd $(srcdir) && TESTDIR='$(CURDIR)' PATH="$(bindir):$$PATH" PGPORT='6$(DEF_PGPORT)' top_builddir='$(CURDIR)/$(top_builddir)' PG_REGRESS='$(CURDIR)/$(top_builddir)/src/test/regress/pg_regress' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) $(if $(PROVE_TESTS),$(PROVE_TESTS),t/*.pl)
 endef
 
 define prove_check
 rm -rf $(CURDIR)/tmp_check/log
-cd $(srcdir) && TESTDIR='$(CURDIR)' $(with_temp_install) PGPORT='6$(DEF_PGPORT)' PG_REGRESS='$(CURDIR)/$(top_builddir)/src/test/regress/pg_regress' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) t/*.pl
+cd $(srcdir) && TESTDIR='$(CURDIR)' $(with_temp_install) PGPORT='6$(DEF_PGPORT)' PG_REGRESS='$(CURDIR)/$(top_builddir)/src/test/regress/pg_regress' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) $(if $(PROVE_TESTS),$(PROVE_TESTS),t/*.pl)
 endef
 
 else

src/test/perl/README

@@ -6,6 +6,12 @@ across the source tree, particularly tests in src/bin and src/test. It's used
 to drive tests for backup and restore, replication, etc - anything that can't
 really be expressed using pg_regress or the isolation test framework.
 
+The tests are invoked via perl's 'prove' command, wrapped in PostgreSQL
+makefiles to handle instance setup etc. See the $(prove_check) and
+$(prove_installcheck) targets in Makefile.global. By default every test in the
+t/ subdirectory is run. Individual test(s) can be run instead by passing
+something like PROVE_TESTS="t/001_testname.pl t/002_othertestname.pl" to make.
+
 You should prefer to write tests using pg_regress in src/test/regress, or
 isolation tester specs in src/test/isolation, if possible. If not, check to
 see if your new tests make sense under an existing tree in src/test, like