Avoid creating testtablespace directories where not wanted.

Recently we refactored things so that pg_regress makes the
"testtablespace" subdirectory used by the core regression tests,
instead of doing that in the makefiles.  That had the undesirable
side effect of making such a subdirectory in every directory that
has "input" or "output" test files.  Since these subdirectories
remain empty, git doesn't complain about them, but nonetheless
they're clutter.

To fix, invent an explicit --make-testtablespace-dir switch,
so that pg_regress only makes the subdirectory when explicitly
told to.

Discussion: https://postgr.es/m/2854388.1621284789@sss.pgh.pa.us

src/test/regress/GNUmakefile

@@ -119,7 +119,8 @@ submake-contrib-spi: | submake-libpgport submake-generated-headers
 ## Run tests
 ##
 
-REGRESS_OPTS = --dlpath=. --max-concurrent-tests=20 $(EXTRA_REGRESS_OPTS)
+REGRESS_OPTS = --dlpath=. --max-concurrent-tests=20 --make-testtablespace-dir \
+	$(EXTRA_REGRESS_OPTS)
 
 check: all
 	$(pg_regress_check) $(REGRESS_OPTS) --schedule=$(srcdir)/parallel_schedule $(MAXCONNOPT) $(EXTRA_TESTS)

src/test/regress/pg_regress.c

@@ -504,25 +504,9 @@ convert_sourcefiles_in(const char *source_subdir, const char *dest_dir, const ch
 	if (!directory_exists(outdir_sub))
 		make_directory(outdir_sub);
 
+	/* We might need to replace @testtablespace@ */
 	snprintf(testtablespace, MAXPGPATH, "%s/testtablespace", outputdir);
 
-	/*
-	 * Clean out the test tablespace dir, or create it if it doesn't exist. On
-	 * Windows, doing this cleanup here makes possible to run the regression
-	 * tests as a Windows administrative user account with the restricted
-	 * token obtained when starting pg_regress.
-	 */
-	if (directory_exists(testtablespace))
-	{
-		if (!rmtree(testtablespace, true))
-		{
-			fprintf(stderr, _("\n%s: could not remove test tablespace \"%s\"\n"),
-					progname, testtablespace);
-			exit(2);
-		}
-	}
-	make_directory(testtablespace);
-
 	/* finally loop on each file and do the replacement */
 	for (name = names; *name; name++)
 	{
@@ -601,6 +585,32 @@ convert_sourcefiles(void)
 	convert_sourcefiles_in("output", outputdir, "expected", "out");
 }
 
+/*
+ * Clean out the test tablespace dir, or create it if it doesn't exist.
+ *
+ * On Windows, doing this cleanup here makes it possible to run the
+ * regression tests under a Windows administrative user account with the
+ * restricted token obtained when starting pg_regress.
+ */
+static void
+prepare_testtablespace_dir(void)
+{
+	char		testtablespace[MAXPGPATH];
+
+	snprintf(testtablespace, MAXPGPATH, "%s/testtablespace", outputdir);
+
+	if (directory_exists(testtablespace))
+	{
+		if (!rmtree(testtablespace, true))
+		{
+			fprintf(stderr, _("\n%s: could not remove test tablespace \"%s\"\n"),
+					progname, testtablespace);
+			exit(2);
+		}
+	}
+	make_directory(testtablespace);
+}
+
 /*
  * Scan resultmap file to find which platform-specific expected files to use.
  *
@@ -2058,6 +2068,7 @@ help(void)
 	printf(_("      --launcher=CMD            use CMD as launcher of psql\n"));
 	printf(_("      --load-extension=EXT      load the named extension before running the\n"));
 	printf(_("                                tests; can appear multiple times\n"));
+	printf(_("      --make-testtablespace-dir create testtablespace directory\n"));
 	printf(_("      --max-connections=N       maximum number of concurrent connections\n"));
 	printf(_("                                (default is 0, meaning unlimited)\n"));
 	printf(_("      --max-concurrent-tests=N  maximum number of concurrent tests in schedule\n"));
@@ -2116,10 +2127,12 @@ regression_main(int argc, char *argv[],
 		{"load-extension", required_argument, NULL, 22},
 		{"config-auth", required_argument, NULL, 24},
 		{"max-concurrent-tests", required_argument, NULL, 25},
+		{"make-testtablespace-dir", no_argument, NULL, 26},
 		{NULL, 0, NULL, 0}
 	};
 
 	bool		use_unix_sockets;
+	bool		make_testtablespace_dir = false;
 	_stringlist *sl;
 	int			c;
 	int			i;
@@ -2245,6 +2258,9 @@ regression_main(int argc, char *argv[],
 			case 25:
 				max_concurrent_tests = atoi(optarg);
 				break;
+			case 26:
+				make_testtablespace_dir = true;
+				break;
 			default:
 				/* getopt_long already emitted a complaint */
 				fprintf(stderr, _("\nTry \"%s -h\" for more information.\n"),
@@ -2297,6 +2313,9 @@ regression_main(int argc, char *argv[],
 	unlimit_core_size();
 #endif
 
+	if (make_testtablespace_dir)
+		prepare_testtablespace_dir();
+
 	if (temp_instance)
 	{
 		FILE	   *pg_conf;

src/tools/msvc/vcregress.pl

@@ -118,6 +118,7 @@ sub installcheck_internal
 		"--bindir=../../../$Config/psql",
 		"--schedule=${schedule}_schedule",
 		"--max-concurrent-tests=20",
+		"--make-testtablespace-dir",
 		"--encoding=SQL_ASCII",
 		"--no-locale");
 	push(@args, $maxconn) if $maxconn;
@@ -152,6 +153,7 @@ sub check
 		"--bindir=",
 		"--schedule=${schedule}_schedule",
 		"--max-concurrent-tests=20",
+		"--make-testtablespace-dir",
 		"--encoding=SQL_ASCII",
 		"--no-locale",
 		"--temp-instance=./tmp_check");