From 0a86d3579edb44ee559cfe6498f43d6637a08bd9 Mon Sep 17 00:00:00 2001
From: Nicholas Marriott <nicm@openbsd.org>
Date: Sat, 6 Feb 2010 18:47:41 +0000
Subject: [PATCH] Change nested check to compare server socket path rather than
 just assuming that if $TMUX is set it is nested. From Micah Cowan.

---
 server-client.c | 11 -----------
 tmux.c          | 17 ++++++++++++++++-
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/server-client.c b/server-client.c
index 34b99514..03560c1c 100644
--- a/server-client.c
+++ b/server-client.c
@@ -693,17 +693,6 @@ server_client_msg_command(struct client *c, struct msg_command_data *data)
 	}
 	cmd_free_argv(argc, argv);
 
-	if (data->pid != -1) {
-		TAILQ_FOREACH(cmd, cmdlist, qentry) {
-			if (cmd->entry->flags & CMD_CANTNEST) {
-				server_client_msg_error(&ctx,
-				    "sessions should be nested with care. "
-				    "unset $TMUX to force");
-				goto error;
-			}
-		}
-	}
-
 	if (cmd_list_exec(cmdlist, &ctx) != 1)
 		server_write_client(c, MSG_EXIT, NULL, 0);
 	cmd_list_free(cmdlist);
diff --git a/tmux.c b/tmux.c
index c6e4f830..a582b951 100644
--- a/tmux.c
+++ b/tmux.c
@@ -484,6 +484,7 @@ main(int argc, char **argv)
 		cmddata.pid = envdata.pid;
 		cmddata.idx = envdata.idx;
 
+		/* Prepare command for server. */
 		cmddata.argc = argc;
 		if (cmd_pack_argv(
 		    argc, argv, cmddata.argv, sizeof cmddata.argv) != 0) {
@@ -499,7 +500,7 @@ main(int argc, char **argv)
 	if (shellcmd != NULL)
 		cmdflags |= CMD_STARTSERVER;
 	else if (argc == 0)	/* new-session is the default */
-		cmdflags |= CMD_STARTSERVER|CMD_SENDENVIRON;
+		cmdflags |= CMD_STARTSERVER|CMD_SENDENVIRON|CMD_CANTNEST;
 	else {
 		/*
 		 * It sucks parsing the command string twice (in client and
@@ -516,10 +517,24 @@ main(int argc, char **argv)
 				cmdflags |= CMD_STARTSERVER;
 			if (cmd->entry->flags & CMD_SENDENVIRON)
 				cmdflags |= CMD_SENDENVIRON;
+			if (cmd->entry->flags & CMD_CANTNEST)
+				cmdflags |= CMD_CANTNEST;
 		}
 		cmd_list_free(cmdlist);
 	}
 
+	/*
+	 * Check if this could be a nested session, if the command can't nest:
+	 * if the socket path matches $TMUX, this is probably the same server.
+	 */
+	if (shellcmd == NULL && envdata.path != NULL &&
+	    cmdflags & CMD_CANTNEST &&
+	    (path == envdata.path || strcmp(path, envdata.path) == 0)) {
+		log_warnx("sessions should be nested with care. "
+		    "unset $TMUX to force.");
+		exit(1);
+	}
+
 	if ((main_ibuf = client_init(path, cmdflags, flags)) == NULL)
 		exit(1);
 	xfree(path);