In this fork, two pull request was made:
1. Making cmd-split-window -v/-h works as expected #1247
2. Making cmd-join-window -bv/-bh works as expected #1263

1. Making cmd-split-window -v/-h works as expected #1247
my suggestion can fix the problem of the split-window command, :

:split-window -v is horisiontal split window actually instead of vertal split window.
:split-window -h is vertical split window actually instead of horisiontal split window.
these action are not as we expected intutively and not consistent with the manual descritipion in the split-window part.
The following are four popular tmux config file in github which are aware of this problem:
gf3/dotfiles(the line 42, and 45) 782 stars on github
tony/tmux-config(line 7) 1135 stars on github
square/maximum-awesome (line 27, 28). 4921 stars
gpakosz/.tmux (line 65, 68). 3735 stars
and the following is a vidwo on youtube realted the problem of split-window command(time-line 1:35):
Create Custom Layout - Linux TMUX
and related tmux config file

2. Making cmd-join-window -bv/-bh works as expected #1263
This problem is similar to pull request 1247, please refer it for more info. The unexpected result can be shown by the following example: if we have two window %0 and %1 in current tmux client , then in the window %0 :

:join-pane -bv -t %1, we get a horisiontal split window instead of a vertical split window as the v in -bv suggested.
:join-pane -bh -t %1. we get a vertical split window instead of a **horisiontal split window as the h in -bh suggested.
just exchange the line 102 and 104 can fix this problem.

the following is from the original tmux project.
========================================================================================================================================
Welcome to tmux!

tmux is a "terminal multiplexer", it enables a number of terminals (or windows)
to be accessed and controlled from a single terminal. tmux is intended to be a
simple, modern, BSD-licensed alternative to programs such as GNU screen.

This release runs on OpenBSD, FreeBSD, NetBSD, Linux, OS X and Solaris.

tmux depends on libevent 2.x. Download it from:

	http:https://libevent.org

It also depends on ncurses, available from:

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To build and install tmux from a release tarball, use:

	$ ./configure && make
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	$ git clone https://github.com/tmux/tmux.git
	$ cd tmux
	$ sh autogen.sh
	$ ./configure && make

(Note that this requires at least a working C compiler, make, autoconf,
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For more information see http:https://git-scm.com. Patches should be sent by email to
the mailing list at [email protected] or submitted through GitHub at
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For documentation on using tmux, see the tmux.1 manpage. It can be viewed from
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	$ nroff -mdoc tmux.1|less

A small example configuration in example_tmux.conf.

And a bash(1) completion file at:

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-- Nicholas Marriott <[email protected]>