Set log_line_prefix and application name in test drivers

Before pg_regress runs psql, set the application name to the test name.
Similarly, set the application name to the test file name in the TAP
tests.  Also, set a default log_line_prefix that show the application
name, as well as the PID and a time stamp.

That way, the server log output can be correlated to the test input
files, making debugging a bit easier.

src/test/perl/PostgresNode.pm

@@ -409,6 +409,7 @@ sub init
 	open my $conf, ">>$pgdata/postgresql.conf";
 	print $conf "\n# Added by PostgresNode.pm\n";
 	print $conf "fsync = off\n";
+	print $conf "log_line_prefix = '%m [%p] %q%a '\n";
 	print $conf "log_statement = all\n";
 	print $conf "port = $port\n";
 

src/test/perl/TestLib.pm

@@ -62,6 +62,8 @@ BEGIN
 	delete $ENV{PGPORT};
 	delete $ENV{PGHOST};
 
+	$ENV{PGAPPNAME} = $0;
+
 	# Must be set early
 	$windows_os = $Config{osname} eq 'MSWin32' || $Config{osname} eq 'msys';
 }

src/test/regress/pg_regress.c

@@ -2270,6 +2270,7 @@ regression_main(int argc, char *argv[], init_function ifunc, test_function tfunc
 		fputs("\n# Configuration added by pg_regress\n\n", pg_conf);
 		fputs("log_autovacuum_min_duration = 0\n", pg_conf);
 		fputs("log_checkpoints = on\n", pg_conf);
+		fputs("log_line_prefix = '%m [%p] %q%a '\n", pg_conf);
 		fputs("log_lock_waits = on\n", pg_conf);
 		fputs("log_temp_files = 128kB\n", pg_conf);
 		fputs("max_prepared_transactions = 2\n", pg_conf);

src/test/regress/pg_regress_main.c

@@ -34,6 +34,7 @@ psql_start_test(const char *testname,
 	char		expectfile[MAXPGPATH];
 	char		psql_cmd[MAXPGPATH * 3];
 	size_t		offset = 0;
+	char	   *appnameenv;
 
 	/*
 	 * Look for files in the output dir first, consistent with a vpath search.
@@ -63,6 +64,9 @@ psql_start_test(const char *testname,
 		offset += snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
 						   "%s ", launcher);
 
+	appnameenv = psprintf("PGAPPNAME=pg_regress/%s", testname);
+	putenv(appnameenv);
+
 	snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
 			 "\"%s%spsql\" -X -a -q -d \"%s\" < \"%s\" > \"%s\" 2>&1",
 			 bindir ? bindir : "",
@@ -80,6 +84,9 @@ psql_start_test(const char *testname,
 		exit(2);
 	}
 
+	unsetenv("PGAPPNAME");
+	free(appnameenv);
+
 	return pid;
 }