Using -l to specify a login shell is non-POSIX and causes problems with shells

that do not support it. Instead, set an empty default-command to invoke $SHELL
with - prefixed to argv[0], and make this the default setting.

tmux.1

@@ -1044,8 +1044,12 @@ maintain this maximum length.
 Set the command used for new windows (if not specified when the window is
 created) to
 .Ar command .
-The default is
+The default is an empty string, which instructs
-.Dq exec $SHELL -l .
+.Nm
+to create a login shell using the
+.Ev SHELL
+environment variable or, if it is unset, the user's shell returned by
+.Xr getpwuid 3 .
 .It Ic default-path Ar path
 Set the default working directory for processes created from keys, or
 interactively from the prompt.

tmux.c

@@ -1,4 +1,4 @@
-/* $Id: tmux.c,v 1.137 2009-06-25 16:56:08 nicm Exp $ */
+/* $Id: tmux.c,v 1.138 2009-07-01 19:42:55 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
@@ -218,7 +218,6 @@ main(int argc, char **argv)
  	struct cmd		*cmd;
 	struct pollfd	 	 pfd;
 	struct hdr	 	 hdr;
-	const char		*shell;
 	struct passwd		*pw;
 	char			*s, *path, *label, *cause, *home, *pass = NULL;
 	char			 cwd[MAXPATHLEN];
@@ -279,6 +278,7 @@ main(int argc, char **argv)
 	options_init(&global_options, NULL);
 	options_set_number(&global_options, "bell-action", BELL_ANY);
 	options_set_number(&global_options, "buffer-limit", 9);
+	options_set_string(&global_options, "default-command", "%s", "");
 	options_set_number(&global_options, "display-time", 750);
 	options_set_number(&global_options, "history-limit", 2000);
 	options_set_number(&global_options, "lock-after-time", 0);
@@ -368,17 +368,6 @@ main(int argc, char **argv)
 	}
 	xfree(label);
 
-	shell = getenv("SHELL");
-	if (shell == NULL || *shell == '\0') {
-		pw = getpwuid(getuid());
-		if (pw != NULL)
-			shell = pw->pw_shell;
-		if (shell == NULL || *shell == '\0')
-			shell = _PATH_BSHELL;
-	}
-	options_set_string(
-	    &global_options, "default-command", "exec %s -l", shell);
-
 	if (getcwd(cwd, sizeof cwd) == NULL) {
 		pw = getpwuid(getuid());
 		if (pw->pw_dir != NULL && *pw->pw_dir != '\0')

window.c

@@ -1,4 +1,4 @@
-/* $Id: window.c,v 1.85 2009-06-25 16:47:00 nicm Exp $ */
+/* $Id: window.c,v 1.86 2009-07-01 19:42:55 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
@@ -22,6 +22,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <fnmatch.h>
+#include <pwd.h>
 #include <signal.h>
 #include <stdint.h>
 #include <stdlib.h>
@@ -53,8 +54,27 @@
 /* Global window list. */
 struct windows windows;
 
+const char	*window_default_command(void);
+
 RB_GENERATE(winlinks, winlink, entry, winlink_cmp);
 
+const char *
+window_default_command(void)
+{
+	const char	*shell;
+	struct passwd	*pw;
+
+	shell = getenv("SHELL");
+	if (shell != NULL && *shell != '\0')
+		return (shell);
+
+	pw = getpwuid(getuid());
+	if (pw != NULL && pw->pw_shell != NULL && *pw->pw_shell != '\0')
+		return (pw->pw_shell);
+
+	return (_PATH_BSHELL);
+}
+
 int
 winlink_cmp(struct winlink *wl1, struct winlink *wl2)
 {
@@ -422,7 +442,8 @@ window_pane_spawn(struct window_pane *wp,
 {
 	struct winsize	 ws;
 	int		 mode;
-	const char     **envq;
+	const char     **envq, *ptr;
+	char		*argv0;
 	struct timeval	 tv;
 
 	if (wp->fd != -1)
@@ -463,7 +484,18 @@ window_pane_spawn(struct window_pane *wp,
 		sigreset();
 		log_close();
 
-		execl(_PATH_BSHELL, "sh", "-c", wp->cmd, (char *) NULL);
+		if (*wp->cmd != '\0') {
+			execl(_PATH_BSHELL, "sh", "-c", wp->cmd, (char *) NULL);
+			fatal("execl failed");
+		}
+
+		/* No command; fork a login shell. */
+		cmd = window_default_command();
+		if ((ptr = strrchr(cmd, '/')) != NULL && *(ptr + 1) != '\0')
+			xasprintf(&argv0, "-%s", ptr + 1);
+		else
+			xasprintf(&argv0, "-%s", cmd);
+		execl(cmd, argv0, (char *) NULL);
 		fatal("execl failed");
 	}