Provide defined ways to set the various default-path possibilities: ~

for home directory, . for server start directory, - for session start
directory and empty for the pane's working directory (the default). All
can also be used as part of a relative path (eg -/foo). Also provide -c
flags to neww and splitw to override default-path setting.

Based on a diff from sthen. ok sthen

cmd-new-window.c

@@ -30,8 +30,9 @@ int	cmd_new_window_exec(struct cmd *, struct cmd_ctx *);
 
 const struct cmd_entry cmd_new_window_entry = {
 	"new-window", "neww",
-	"adkn:Pt:", 0, 1,
-	"[-adk] [-n window-name] [-t target-window] [command]",
+	"ac:dkn:Pt:", 0, 1,
+	"[-adk] [-c start-directory] [-n window-name] [-t target-window] "
+	"[command]",
 	0,
 	NULL,
 	NULL,
@@ -99,7 +100,7 @@ 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 = cmd_get_default_path(ctx);
+	cwd = cmd_get_default_path(ctx, args_get(args, 'c'));
 
 	if (idx == -1)
 		idx = -1 - options_get_number(&s->options, "base-index");

cmd-split-window.c

@@ -33,8 +33,9 @@ int	cmd_split_window_exec(struct cmd *, struct cmd_ctx *);
 
 const struct cmd_entry cmd_split_window_entry = {
 	"split-window", "splitw",
-	"dl:hp:Pt:v", 0, 1,
-	"[-dhvP] [-p percentage|-l size] [-t target-pane] [command]",
+	"c:dl:hp:Pt:v", 0, 1,
+	"[-dhvP] [-c start-directory] [-p percentage|-l size] [-t target-pane] "
+	"[command]",
 	0,
 	cmd_split_window_key_binding,
 	NULL,
@@ -78,7 +79,7 @@ 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 = cmd_get_default_path(ctx);
+	cwd = cmd_get_default_path(ctx, args_get(args, 'c'));
 
 	type = LAYOUT_TOPBOTTOM;
 	if (args_has(args, 'h'))

cmd.c

@@ -21,6 +21,7 @@
 
 #include <fnmatch.h>
 #include <paths.h>
+#include <pwd.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -1251,34 +1252,82 @@ cmd_template_replace(char *template, const char *s, int idx)
 	return (buf);
 }
 
-/* Return the default path for a new pane. */
+/*
+ * Return the default path for a new pane, using the given path or the
+ * default-path option if it is NULL. Several special values are accepted: the
+ * empty string or relative path for the current pane's working directory, ~
+ * for the user's home, - for the session working directory, . for the tmux
+ * server's working directory. The default on failure is the session's working
+ * directory.
+ */
 const char *
-cmd_get_default_path(struct cmd_ctx *ctx)
+cmd_get_default_path(struct cmd_ctx *ctx, const char *cwd)
 {
-	const char		*cwd;
 	struct session		*s;
-	struct window_pane	*wp;
 	struct environ_entry	*envent;
+	const char		*root;
+	char			 tmp[MAXPATHLEN];
+	struct passwd		*pw;
+	int			 n;
+	size_t			 skip;
+	static char		 path[MAXPATHLEN];
 
 	if ((s = cmd_current_session(ctx, 0)) == NULL)
 		return (NULL);
 
-	cwd = options_get_string(&s->options, "default-path");
-	if ((cwd[0] == '~' && cwd[1] == '\0') || !strcmp(cwd, "$HOME")) {
-		envent = environ_find(&global_environ, "HOME");
-		if (envent != NULL && *envent->value != '\0')
-			return envent->value;
-		cwd = "";
-	}
-	if (*cwd == '\0') {
-		if (ctx->cmdclient != NULL && ctx->cmdclient->cwd != NULL)
-			return (ctx->cmdclient->cwd);
-		if (ctx->curclient != NULL) {
-			wp = s->curw->window->active;
-			if ((cwd = get_proc_cwd(wp->pid)) != NULL)
-				return (cwd);
+	if (cwd == NULL)
+		cwd = options_get_string(&s->options, "default-path");
+
+	skip = 1;
+	if (strcmp(cwd, "$HOME") == 0 || strncmp(cwd, "$HOME/", 6) == 0) {
+		/* User's home directory - $HOME. */
+		skip = 5;
+		goto find_home;
+	} else if (cwd[0] == '~' && (cwd[1] == '\0' || cwd[1] == '/')) {
+		/* User's home directory - ~. */
+		goto find_home;
+	} else if (cwd[0] == '-' && (cwd[1] == '\0' || cwd[1] == '/')) {
+		/* Session working directory. */
+		root = s->cwd;
+		goto complete_path;
+	} else if (cwd[0] == '.' && (cwd[1] == '\0' || cwd[1] == '/')){
+		/* Server working directory. */
+		if (getcwd(tmp, sizeof tmp) != NULL) {
+			root = tmp;
+			goto complete_path;
 		}
 		return (s->cwd);
+	} else if (*cwd == '/') {
+		/* Absolute path. */
+		return (cwd);
+	} else {
+		/* Empty or relative path. */
+		if (ctx->cmdclient != NULL && ctx->cmdclient->cwd != NULL)
+			root = ctx->cmdclient->cwd;
+		else if (ctx->curclient != NULL)
+			root = get_proc_cwd(s->curw->window->active->pid);
+		else
+			return (s->cwd);
+		skip = 0;
+		goto complete_path;
 	}
-	return (cwd);
+
+	return (s->cwd);
+
+find_home:
+	envent = environ_find(&global_environ, "HOME");
+	if (envent != NULL && *envent->value != '\0')
+		root = envent->value;
+	else if ((pw = getpwuid(getuid())) != NULL)
+		root = pw->pw_dir;
+	else
+		return (s->cwd);
+
+complete_path:
+	if (root[skip] == '\0')
+		return (root);
+	n = snprintf(path, sizeof path, "%s/%s", root, cwd + skip);
+	if (n > 0 && (size_t)n < sizeof path)
+		return (path);
+	return (s->cwd);
 }

tmux.1

@@ -1224,6 +1224,7 @@ is moved to
 .Ar dst-window .
 .It Xo Ic new-window
 .Op Fl adkP
+.Op Fl c Ar start-directory
 .Op Fl n Ar window-name
 .Op Fl t Ar target-window
 .Op Ar shell-command
@@ -1254,6 +1255,15 @@ If
 is not specified, the value of the
 .Ic default-command
 option is used.
+.Fl c
+specifies the working directory in which the new window is created.
+It may have an absolute path or one of the following values (or a subdirectory):
+.Bl -column "XXXXXXXXXXXX" "XXXXXXXXXXXXXXXXXXXXXXXX" -offset indent
+.It Li "Empty string" Ta "Current pane's directory"
+.It Li "~" Ta "User's home directory"
+.It Li "-" Ta "Where session was started"
+.It Li "." Ta "Where server was started"
+.El
 .Pp
 When the shell command completes, the window closes.
 See the
@@ -1453,6 +1463,7 @@ and
 commands.
 .It Xo Ic split-window
 .Op Fl dhvP
+.Op Fl c Ar start-directory
 .Oo Fl l
 .Ar size |
 .Fl p Ar percentage Oc

tmux.h

@@ -1559,7 +1559,7 @@ 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);
-const char     	*cmd_get_default_path(struct cmd_ctx *ctx);
+const char     	*cmd_get_default_path(struct cmd_ctx *, const char *);
 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;