Change the way the working directory for new processes is discovered. If

default-path isn't empty, it is used. Otherwise:

1) If tmux neww is run from the command line, the working directory of the
   client is used.

2) Otherwise sysctl KERN_PROC_CWD is used to retrieve the current
   working directory of the process in the active pane.

3) If that fails, the directory where the session was created is used.

Support code by Romain Francois, OpenBSD specific bits by me.

Note this requires a recent userland and kernel with KERN_PROC_CWD.

cmd-new-window.c

@@ -98,13 +98,7 @@ cmd_new_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 		cmd = options_get_string(&s->options, "default-command");
 	else
 		cmd = args->argv[0];
-	cwd = options_get_string(&s->options, "default-path");
-	if (*cwd == '\0') {
-		if (ctx->cmdclient != NULL && ctx->cmdclient->cwd != NULL)
-			cwd = ctx->cmdclient->cwd;
-		else
-			cwd = s->cwd;
-	}
+	cwd = cmd_get_default_path(ctx);
 
 	if (idx == -1)
 		idx = -1 - options_get_number(&s->options, "base-index");

cmd-split-window.c

@@ -78,13 +78,7 @@ cmd_split_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 		cmd = options_get_string(&s->options, "default-command");
 	else
 		cmd = args->argv[0];
-	cwd = options_get_string(&s->options, "default-path");
-	if (*cwd == '\0') {
-		if (ctx->cmdclient != NULL && ctx->cmdclient->cwd != NULL)
-			cwd = ctx->cmdclient->cwd;
-		else
-			cwd = s->cwd;
-	}
+	cwd = cmd_get_default_path(ctx);
 
 	type = LAYOUT_TOPBOTTOM;
 	if (args_has(args, 'h'))

cmd.c

@@ -1213,3 +1213,28 @@ cmd_template_replace(char *template, const char *s, int idx)
 
 	return (buf);
 }
+
+/* Return the default path for a new pane. */
+char *
+cmd_get_default_path(struct cmd_ctx *ctx)
+{
+	char			*cwd;
+	struct session		*s;
+	struct window_pane	*wp;
+
+	if ((s = cmd_current_session(ctx, 0)) == NULL)
+		return (NULL);
+
+	cwd = options_get_string(&s->options, "default-path");
+	if (*cwd == '\0') {
+		if (ctx->cmdclient != NULL && ctx->cmdclient->cwd != NULL)
+			return (ctx->cmdclient->cwd);
+		if (ctx->curclient != NULL) {
+			wp = s->curw->window->active;
+			if ((cwd = get_proc_cwd(wp->pid)) != NULL)
+				return (cwd);
+		}
+		return (s->cwd);
+	}
+	return (cwd);
+}

procname.c

@@ -35,7 +35,8 @@
 	((p)->p_stat == SSTOP || (p)->p_stat == SZOMB || (p)->p_stat == SDEAD)
 
 struct kinfo_proc	*cmp_procs(struct kinfo_proc *, struct kinfo_proc *);
-char		*get_proc_name(int, char *);
+char			*get_proc_name(int, char *);
+char			*get_proc_cwd(pid_t);
 
 struct kinfo_proc *
 cmp_procs(struct kinfo_proc *p1, struct kinfo_proc *p2)
@@ -130,3 +131,15 @@ error:
 	free(buf);
 	return (NULL);
 }
+
+char*
+get_proc_cwd(pid_t pid)
+{
+	int		name[] = { CTL_KERN, KERN_PROC_CWD, (int)pid };
+	static char	path[MAXPATHLEN];
+	size_t		pathlen = sizeof path;
+
+	if (sysctl(name, 3, path, &pathlen, NULL, 0) != 0)
+		return (NULL);
+	return (path);
+}

tmux.1

@@ -1841,10 +1841,10 @@ to create a login shell using the value of the
 .Ic default-shell
 option.
 .It Ic default-path Ar path
-Set the default working directory for processes created from keys, or
-interactively from the prompt.
-The default is empty, which means to use the working directory of the shell
-from which the server was started if it is available or the user's home if not.
+Set the default working directory for new panes.
+If empty (the default), the working directory is determined from the process
+running in the active pane, from the command line environment or from the
+working directory where the session was created.
 .It Ic default-shell Ar path
 Specify the default shell.
 This is used as the login shell for new windows when the

tmux.h

@@ -1562,6 +1562,7 @@ int		 cmd_find_index(
 struct winlink	*cmd_find_pane(struct cmd_ctx *,
 		     const char *, struct session **, struct window_pane **);
 char		*cmd_template_replace(char *, const char *, int);
+char		*cmd_get_default_path(struct cmd_ctx *ctx);
 extern const struct cmd_entry *cmd_table[];
 extern const struct cmd_entry cmd_attach_session_entry;
 extern const struct cmd_entry cmd_bind_key_entry;
@@ -2079,6 +2080,7 @@ u_int	utf8_split2(u_int, u_char *);
 
 /* procname.c */
 char   *get_proc_name(int, char *);
+char   *get_proc_cwd(pid_t);
 
 /* log.c */
 void		 log_open_tty(int);