'zic' now rejects output file names with '.' or '..' components.

* zic.8, NEWS: Say that "." and ".." file name
components are not allowed in output file names.
* zic.c (componentcheck, namecheck): Do not allow such
file name components.

NEWS

@@ -19,6 +19,9 @@ Unreleased, experimental changes
     Error diagnostics of 'zic' and 'yearistype' have been reworded so that
     they no longer use ASCII '-' as if it were a dash.
 
+    'zic' now rejects output file names that contain '.' or '..' components.
+    (Thanks to Tim Parenti for reporting the problem.)
+
     'zic -v' now warns about output file names that do not follow
     POSIX rules, or that contain a digit or '.'.  (Thanks to Arthur
     David Olson for starting the ball rolling on this.)

zic.8

@@ -339,6 +339,12 @@ The fields that make up a zone line are:
 The name of the time zone.
 This is the name used in creating the time conversion information file for the
 zone.
+It should not contain a file name component
+.q ".\&"
+or
+.q ".." ;
+a file name component is a maximal substring that does not contain
+.q "/" .
 .TP
 .B GMTOFF
 The amount of time to add to UT to get standard time in this zone.
@@ -408,10 +414,13 @@ The
 .B LINK-FROM
 field should appear as the
 .B NAME
-field in some zone line;
-the
+field in some zone line.
+The
 .B LINK-TO
-field is used as an alternate name for that zone.
+field is used as an alternate name for that zone;
+it has the same syntax as a zone line's
+.B NAME
+field.
 .PP
 Except for continuation lines,
 lines may appear in any order in the input.

zic.c

@@ -615,6 +615,15 @@ componentcheck(char const *name, char const *component,
 {
 	enum { component_len_max = 14 };
 	size_t component_len = component_end - component;
+	if (0 < component_len && component_len <= 2
+	    && component[0] == '.' && component_end[-1] == '.') {
+		fprintf(stderr, _("%s: file name '%s' contains"
+				  " '%.*s' component"),
+			progname, name, (int) component_len, component);
+		exit(EXIT_FAILURE);
+	}
+	if (!noise)
+		return;
 	if (0 < component_len && component[0] == '-')
 		warning(_("file name '%s' component contains leading '-'"),
 			name);
@@ -641,11 +650,9 @@ namecheck(const char *name)
 	  " !\"#$%&'()*+,.0123456789:;<=>?@[\\]^`{|}~";
 
 	register char const *component = name;
-	if (!noise)
-		return;
 	for (cp = name; *cp; cp++) {
 		unsigned char c = *cp;
-		if (!strchr(benign, c)) {
+		if (noise && !strchr(benign, c)) {
 			warning((strchr(printable_and_not_benign, c)
 				 ? _("file name '%s' contains byte '%c'")
 				 : _("file name '%s' contains byte '\\%o'")),