Add a height option to `Copen`

[shym]

copen command can take a height option for the quickfix window and, as far as I can tell, that height is preserved until the next explicit invocation of copen.
Could Copen provide the same option and behaviour?

By the way, for consistency, it would be great for that height to be used also for tmux splits.

[eremite]

let g:dispatch_quickfix_height=20
let g:dispatch_tmux_height=20

That may not help you, but it helped me.

[tpope]

Circling back to the original post, I'd entertain a PR that added -count to :Copen.

[tpope]

By the way I'm changing it so you only have to set g:dispatch_quickfix_height, because forcing you to set both options to the same value is a waste of everyone's time.

[shym]

When I opened this issue, those configuration variables were not available yet, so I proposed something as close as possible to the standard vim command. But I’ve been using the configuration variables since they were merged in. It’s probably handier to have variables and using copen to adjust the size when needed, by the way.

Edit: after using for a few days the patch in #207, I find it a nice complement to the setting.