Added support for a %H escape in the value of the RSYNC_CONNECT_PROG

environment variable.

socket.c

@@ -300,6 +300,42 @@ int open_socket_out_wrapped(char *host, int port, const char *bind_addr,
 {
 	char *prog = getenv("RSYNC_CONNECT_PROG");
 
+	if (strchr(prog, '%')) {
+		int hlen = strlen(host);
+		int len = strlen(prog) + 1;
+		char *f, *t;
+		for (f = prog; *f; f++) {
+			if (*f != '%')
+				continue;
+			/* Compute more than enough room. */
+			if (f[1] == '%')
+				f++;
+			else
+				len += hlen;
+		}
+		f = prog;
+		if (!(prog = new_array(char, len)))
+			out_of_memory("open_socket_out_wrapped");
+		for (t = prog; *f; f++) {
+			if (*f == '%') {
+				switch (*++f) {
+				case '%':
+					/* Just skips the extra '%'. */
+					break;
+				case 'H':
+					memcpy(t, host, hlen);
+					t += hlen;
+					continue;
+				default:
+					f--; /* pass % through */
+					break;
+				}
+			}
+			*t++ = *f;
+		}
+		*t = '\0';
+	}
+
 	if (verbose >= 2) {
 		rprintf(FINFO, "%sopening tcp connection to %s port %d\n",
 			prog ? "Using RSYNC_CONNECT_PROG instead of " : "",