mdocml: Improve handling of the roff(7) "\t" escape sequence: * Parsing

[schwarze@mdocml.bsd.lv]

Log Message:
-----------
Improve handling of the roff(7) "\t" escape sequence:
* Parsing macro arguments has to be done in copy mode,
  which implies replacing "\t" by a literal tab character.
* Otherwise, render "\t" as the empty string, not as a 't' character.

This fixes formatting of the distfile example in the oldrdist(1) manual.
This also shows up in the unzip(1) manual as one of several issues 
preventing the removal of USE_GROFF from the archivers/unzip port.
Thanks to espie@ for attracting my attention to the unzip(1) manual.

Modified Files:
--------------
    mdocml:
        chars.c
        chars.in
        mandoc.c

Revision Data
-------------
Index: mandoc.c
===================================================================
RCS file: /usr/vhosts/mdocml.bsd.lv/cvs/mdocml/mandoc.c,v
retrieving revision 1.66
retrieving revision 1.67
diff -Lmandoc.c -Lmandoc.c -u -p -r1.66 -r1.67
--- mandoc.c
+++ mandoc.c
@@ -432,17 +432,35 @@ mandoc_getarg(struct mparse *parse, char
 	pairs = 0;
 	white = 0;
 	for (cp = start; '\0' != *cp; cp++) {
-		/* Move left after quoted quotes and escaped backslashes. */
+
+		/*
+		 * Move the following text left
+		 * after quoted quotes and after "\\" and "\t".
+		 */
 		if (pairs)
 			cp[-pairs] = cp[0];
+
 		if ('\\' == cp[0]) {
-			if ('\\' == cp[1]) {
-				/* Poor man's copy mode. */
+			/*
+			 * In copy mode, translate double to single
+			 * backslashes and backslash-t to literal tabs.
+			 */
+			switch (cp[1]) {
+			case ('t'):
+				cp[0] = '\t';
+				/* FALLTHROUGH */
+			case ('\\'):
 				pairs++;
 				cp++;
-			} else if (0 == quoted && ' ' == cp[1])
+				break;
+			case (' '):
 				/* Skip escaped blanks. */
-				cp++;
+				if (0 == quoted)
+					cp++;
+				break;
+			default:
+				break;
+			}
 		} else if (0 == quoted) {
 			if (' ' == cp[0]) {
 				/* Unescaped blanks end unquoted args. */
Index: chars.c
===================================================================
RCS file: /usr/vhosts/mdocml.bsd.lv/cvs/mdocml/chars.c,v
retrieving revision 1.53
retrieving revision 1.54
diff -Lchars.c -Lchars.c -u -p -r1.53 -r1.54
--- chars.c
+++ chars.c
@@ -37,7 +37,7 @@ struct	ln {
 	int		  unicode;
 };
 
-#define	LINES_MAX	  328
+#define	LINES_MAX	  329
 
 #define CHAR(in, ch, code) \
 	{ NULL, (in), (ch), (code) },
Index: chars.in
===================================================================
RCS file: /usr/vhosts/mdocml.bsd.lv/cvs/mdocml/chars.in,v
retrieving revision 1.42
retrieving revision 1.43
diff -Lchars.in -Lchars.in -u -p -r1.42 -r1.43
--- chars.in
+++ chars.in
@@ -42,6 +42,7 @@ CHAR("&",			"",		0)
 CHAR("^",			"",		0)
 CHAR("|",			"",		0)
 CHAR("}",			"",		0)
+CHAR("t",			"",		0)
 
 /* Accents. */
 CHAR("a\"",			"\"",		779)
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