Add terminal_supports_color(), used by logging to terminal code.

We now also correctly disable color support if someone is on
a color-capable terminal but redirects the output of the boot
to a file, eg: bin/unrealircd >boot.log 2>&1

include/h.h

@@ -1054,6 +1054,7 @@ extern char *get_connect_extinfo(Client *client);
 extern char *unreal_strftime(char *str);
 extern void strtolower_safe(char *dst, char *src, int size);
 extern int running_interactively(void);
+extern int terminal_supports_color(void);
 extern void skip_whitespace(char **p);
 extern void read_until(char **p, char *stopchars);
 /* src/unrealdb.c start */

src/log.c

@@ -1044,9 +1044,7 @@ void do_unreal_log_disk(LogLevel loglevel, char *subsystem, char *event_id, Mult
 			else
 				win_log("* [%s] %s\n", log_level_valtostring(loglevel), m->line);
 #else
-			char *t = getenv("TERM");
-			/* Very lazy color detection */
-			if (t && strstr(t, "color"))
+			if (terminal_supports_color())
 			{
 				if (show_event_id_console)
 				{

src/misc.c

@@ -2129,6 +2129,34 @@ int running_interactively(void)
 #endif
 }
 
+int terminal_supports_color(void)
+{
+#ifndef _WIN32
+	char *s;
+
+	/* Yeah we check all of stdin, stdout, stderr, because
+	 * or more may be redirected (bin/unrealircd >log 2>&1),
+	 * and then we want to say no to color support.
+	 */
+	if (!isatty(0) || !isatty(1) || !isatty(2))
+		return 0;
+
+	s = getenv("TERM");
+	/* Yeah this is a lazy way to detect color-capable terminals
+	 * but it is good enough for me.
+	 */
+	if (s)
+	{
+		if (strstr(s, "color") || strstr(s, "ansi"))
+			return 1;
+	}
+
+	return 0;
+#else
+	return 0;
+#endif
+}
+
 /** Skip whitespace (if any) */
 void skip_whitespace(char **p)
 {