add an implicit fastcgi parameter: GEMINI_SEARCH_STRING

it’s the QUERY_STRING decoded if it’s a search-string (i.e. not a
key-value pair.)  It’s useful for scripts to avoid percent-decoding
the querystring in the most common case of a query, because in Gemini
querystrings key-value paired are not common.

Idea from a discussion with Allen Sobot.

fcgi.c

@@ -344,6 +344,7 @@ void
 fcgi_req(struct client *c)
 {
 	char		 addr[NI_MAXHOST], buf[22];
+	char		*qs;
 	int		 e;
 	time_t		 tim;
 	struct tm	 tminfo;
@@ -368,6 +369,14 @@ fcgi_req(struct client *c)
 	fcgi_send_param(c->cgibev, "SERVER_PROTOCOL", "GEMINI");
 	fcgi_send_param(c->cgibev, "SERVER_SOFTWARE", GMID_VERSION);
 
+	if (*c->iri.query != '\0' &&
+	    strchr(c->iri.query, '=') == NULL &&
+	    (qs = strdup(c->iri.query)) != NULL) {
+		pct_decode_str(qs);
+		fcgi_send_param(c->cgibev, "GEMINI_SEARCH_STRING", qs);
+		free(qs);
+	}
+
 	TAILQ_FOREACH(p, &c->host->params, envs) {
 		fcgi_send_param(c->cgibev, p->name, p->value);
 	}

gmid.conf.5

@@ -286,6 +286,12 @@ Full path to the FastCGI script being executed.
 The full IRI of the request.
 .It Ev GEMINI_URL_PATH
 The path of the request.
+.It Ev GEMINI_SEARCH_STRING
+The decoded
+.Ev QUERY_STRING
+if defined in the request and if it doesn't contain any unencoded
+.Sq =
+characters, otherwise unset.
 .It Ev PATH_INFO
 The portion of the requested path that is derived from the the IRI
 path hierarchy following the part that identifies the script itself.

iri.c

@@ -488,7 +488,9 @@ pct_decode_str(char *s)
 	char *t;
 
 	for (t = s; *t; ++t) {
-		if (*t == '%' && valid_pct_enc_string(t))
+		if (*t == '+')
+			*t = ' ';
+		else if (*t == '%' && valid_pct_enc_string(t))
 			pct_decode(t);
 	}