For studying the differences between prior tmux versions to check compatibility with legacy versions.
Get source:
$ git clone https://github.com/tmux/tmux
$ cd tmux
Converted with:
$ git checkout <version>
$ ./autogen.sh
$ ./configure
$ make
$ groff -t -e -mandoc -Tascii tmux.1 | col -bx > manpage.txt
repeat for versions.
Create a git-diff style diff of version manuals:
$ diff -u manual/1.6.txt manual/1.8.txt