Add CSV table output mode in psql.

"\pset format csv", or --csv, selects comma-separated values table format.
This is compliant with RFC 4180, except that we aren't too picky about
whether the record separator is LF or CRLF; also, the user may choose a
field separator other than comma.

This output format is directly compatible with the server's COPY CSV
format, and will also be useful as input to other programs.  It's
considerably safer for that purpose than the old recommendation to
use "unaligned" format, since the latter couldn't handle data
containing the field separator character.

Daniel Vérité, reviewed by Fabien Coelho and David Fetter, some
tweaking by me

Discussion: https://postgr.es/m/a8de371e-006f-4f92-ab72-2bbe3ee78f03@manitou-mail.org

src/fe_utils/print.c

@@ -1737,7 +1737,119 @@ print_aligned_vertical(const printTableContent *cont,
 
 
 /**********************/
-/* HTML printing ******/
+/* CSV format		  */
+/**********************/
+
+
+static void
+csv_escaped_print(const char *str, FILE *fout)
+{
+	const char *p;
+
+	fputc('"', fout);
+	for (p = str; *p; p++)
+	{
+		if (*p == '"')
+			fputc('"', fout);	/* double quotes are doubled */
+		fputc(*p, fout);
+	}
+	fputc('"', fout);
+}
+
+static void
+csv_print_field(const char *str, FILE *fout, char sep)
+{
+	/*----------------
+	 * Enclose and escape field contents when one of these conditions is met:
+	 * - the field separator is found in the contents.
+	 * - the field contains a CR or LF.
+	 * - the field contains a double quote.
+	 * - the field is exactly "\.".
+	 * - the field separator is either "\" or ".".
+	 * The last two cases prevent producing a line that the server's COPY
+	 * command would interpret as an end-of-data marker.  We only really
+	 * need to ensure that the complete line isn't exactly "\.", but for
+	 * simplicity we apply stronger restrictions here.
+	 *----------------
+	 */
+	if (strchr(str, sep) != NULL ||
+		strcspn(str, "\r\n\"") != strlen(str) ||
+		strcmp(str, "\\.") == 0 ||
+		sep == '\\' || sep == '.')
+		csv_escaped_print(str, fout);
+	else
+		fputs(str, fout);
+}
+
+static void
+print_csv_text(const printTableContent *cont, FILE *fout)
+{
+	const char *const *ptr;
+	int			i;
+
+	if (cancel_pressed)
+		return;
+
+	/*
+	 * The title and footer are never printed in csv format. The header is
+	 * printed if opt_tuples_only is false.
+	 *
+	 * Despite RFC 4180 saying that end of lines are CRLF, terminate lines
+	 * with '\n', which prints out as the system-dependent EOL string in text
+	 * mode (typically LF on Unix and CRLF on Windows).
+	 */
+	if (cont->opt->start_table && !cont->opt->tuples_only)
+	{
+		/* print headers */
+		for (ptr = cont->headers; *ptr; ptr++)
+		{
+			if (ptr != cont->headers)
+				fputc(cont->opt->csvFieldSep[0], fout);
+			csv_print_field(*ptr, fout, cont->opt->csvFieldSep[0]);
+		}
+		fputc('\n', fout);
+	}
+
+	/* print cells */
+	for (i = 0, ptr = cont->cells; *ptr; i++, ptr++)
+	{
+		csv_print_field(*ptr, fout, cont->opt->csvFieldSep[0]);
+		if ((i + 1) % cont->ncolumns)
+			fputc(cont->opt->csvFieldSep[0], fout);
+		else
+			fputc('\n', fout);
+	}
+}
+
+static void
+print_csv_vertical(const printTableContent *cont, FILE *fout)
+{
+	const char *const *ptr;
+	int			i;
+
+	/* print records */
+	for (i = 0, ptr = cont->cells; *ptr; i++, ptr++)
+	{
+		if (cancel_pressed)
+			return;
+
+		/* print name of column */
+		csv_print_field(cont->headers[i % cont->ncolumns], fout,
+						cont->opt->csvFieldSep[0]);
+
+		/* print field separator */
+		fputc(cont->opt->csvFieldSep[0], fout);
+
+		/* print field value */
+		csv_print_field(*ptr, fout, cont->opt->csvFieldSep[0]);
+
+		fputc('\n', fout);
+	}
+}
+
+
+/**********************/
+/* HTML				  */
 /**********************/
 
 
@@ -1953,9 +2065,10 @@ print_html_vertical(const printTableContent *cont, FILE *fout)
 
 
 /*************************/
-/* ASCIIDOC		 */
+/* ASCIIDOC				 */
 /*************************/
 
+
 static void
 asciidoc_escaped_print(const char *in, FILE *fout)
 {
@@ -2174,6 +2287,7 @@ print_asciidoc_vertical(const printTableContent *cont, FILE *fout)
 	}
 }
 
+
 /*************************/
 /* LaTeX				 */
 /*************************/
@@ -2319,6 +2433,11 @@ print_latex_text(const printTableContent *cont, FILE *fout)
 }
 
 
+/*************************/
+/* LaTeX longtable		 */
+/*************************/
+
+
 static void
 print_latex_longtable_text(const printTableContent *cont, FILE *fout)
 {
@@ -2564,7 +2683,7 @@ print_latex_vertical(const printTableContent *cont, FILE *fout)
 
 
 /*************************/
-/* Troff -ms		 */
+/* Troff -ms			 */
 /*************************/
 
 
@@ -3234,6 +3353,12 @@ printTable(const printTableContent *cont,
 			else
 				print_aligned_text(cont, fout, is_pager);
 			break;
+		case PRINT_CSV:
+			if (cont->opt->expanded == 1)
+				print_csv_vertical(cont, fout);
+			else
+				print_csv_text(cont, fout);
+			break;
 		case PRINT_HTML:
 			if (cont->opt->expanded == 1)
 				print_html_vertical(cont, fout);