Add new ECHO mode 'errors' that displays only failed commands in psql.

When the psql variable ECHO is set to 'erros', only failed SQL commands
are printed to standard error output. Also this patch adds -b option into psql.
This is equivalent to setting the variable ECHO to 'errors'.

Pavel Stehule, reviewed by Fabrízio de Royes Mello, Samrat Revagade,
Kumar Rajeev Rastogi, Abhijit Menon-Sen, and me.

doc/src/sgml/ref/psql-ref.sgml

@@ -72,6 +72,18 @@ PostgreSQL documentation
       </listitem>
     </varlistentry>
 
+    <varlistentry>
+      <term><option>-b</></term>
+      <term><option>--echo-errors</></term>
+      <listitem>
+      <para>
+      Print failed SQL commands to standard error output. This is
+      equivalent to setting the variable <varname>ECHO</varname> to
+      <literal>errors</literal>.
+      </para>
+      </listitem>
+    </varlistentry>
+
     <varlistentry>
       <term><option>-c <replaceable class="parameter">command</replaceable></></term>
       <term><option>--command=<replaceable class="parameter">command</replaceable></></term>
@@ -2812,7 +2824,9 @@ bar
         <literal>queries</literal>,
         <application>psql</application> merely prints all queries as
         they are sent to the server. The switch for this is
-        <option>-e</option>.
+        <option>-e</option>. If set to <literal>errors</literal> then only
+        failed queries are displayed on standard error output. The switch
+        for this is <option>-b</option>.
         </para>
         </listitem>
       </varlistentry>

src/bin/psql/common.c

@@ -995,6 +995,9 @@ SendQuery(const char *query)
 		results = NULL;			/* PQclear(NULL) does nothing */
 	}
 
+	if (!OK && pset.echo == PSQL_ECHO_ERRORS)
+		psql_error("STATEMENT:  %s\n", query);
+
 	/* If we made a temporary savepoint, possibly release/rollback */
 	if (on_error_rollback_savepoint)
 	{

src/bin/psql/help.c

@@ -87,6 +87,7 @@ usage(void)
 
 	printf(_("\nInput and output options:\n"));
 	printf(_("  -a, --echo-all           echo all input from script\n"));
+	printf(_("  -b, --echo-errors        echo failed commands\n"));
 	printf(_("  -e, --echo-queries       echo commands sent to server\n"));
 	printf(_("  -E, --echo-hidden        display queries that internal commands generate\n"));
 	printf(_("  -L, --log-file=FILENAME  send session log to file\n"));

src/bin/psql/settings.h

@@ -31,6 +31,7 @@ typedef enum
 {
 	PSQL_ECHO_NONE,
 	PSQL_ECHO_QUERIES,
+	PSQL_ECHO_ERRORS,
 	PSQL_ECHO_ALL
 } PSQL_ECHO;
 

src/bin/psql/startup.c

@@ -354,6 +354,7 @@ parse_psql_options(int argc, char *argv[], struct adhoc_opts * options)
 		{"command", required_argument, NULL, 'c'},
 		{"dbname", required_argument, NULL, 'd'},
 		{"echo-queries", no_argument, NULL, 'e'},
+		{"echo-errors", no_argument, NULL, 'b'},
 		{"echo-hidden", no_argument, NULL, 'E'},
 		{"file", required_argument, NULL, 'f'},
 		{"field-separator", required_argument, NULL, 'F'},
@@ -391,7 +392,7 @@ parse_psql_options(int argc, char *argv[], struct adhoc_opts * options)
 
 	memset(options, 0, sizeof *options);
 
-	while ((c = getopt_long(argc, argv, "aAc:d:eEf:F:h:HlL:no:p:P:qR:sStT:U:v:VwWxXz?01",
+	while ((c = getopt_long(argc, argv, "aAbc:d:eEf:F:h:HlL:no:p:P:qR:sStT:U:v:VwWxXz?01",
 							long_options, &optindex)) != -1)
 	{
 		switch (c)
@@ -402,6 +403,9 @@ parse_psql_options(int argc, char *argv[], struct adhoc_opts * options)
 			case 'A':
 				pset.popt.topt.format = PRINT_UNALIGNED;
 				break;
+			case 'b':
+				SetVariable(pset.vars, "ECHO", "errors");
+				break;
 			case 'c':
 				options->action_string = pg_strdup(optarg);
 				if (optarg[0] == '\\')
@@ -720,6 +724,8 @@ echo_hook(const char *newval)
 		pset.echo = PSQL_ECHO_NONE;
 	else if (strcmp(newval, "queries") == 0)
 		pset.echo = PSQL_ECHO_QUERIES;
+	else if (strcmp(newval, "errors") == 0)
+		pset.echo = PSQL_ECHO_ERRORS;
 	else if (strcmp(newval, "all") == 0)
 		pset.echo = PSQL_ECHO_ALL;
 	else