options with a single foo-style option. For example:
set -g status-fg yellow
set -g status-bg red
set -g status-attr blink
Becomes:
set -g status-style fg=yellow,bg=red,blink
The -a flag to set can be used to add to rather than replace a style. So:
set -g status-bg red
Becomes:
set -ag status-style bg=red
Currently this is fully backwards compatible (all *-{fg,bg,attr} options
remain) but the plan is to deprecate them over time.
From Tiago Cunha.