Feature: Duplicate and mirror on all and selected outputs

[Ventto]

Let's say, we have a laptop with two plugged-in monitors. At start, only the primary one is turned on:

$ mons
Monitors: 3
Mode: primary
0:  eDP1      (enabled)
2:  HDMI1     
3:  DP1

We want to duplicate our desktop view on every output:

$ mons -D
$ mons
Monitors: 4
Mode: duplicate
0:  eDP1      (enabled)
2:  HDMI1     (enabled)
3:  DP1       (enabled)

Or by selection:

$ mons -o
$ mons
Monitors: 3
Mode: duplicate
0:  eDP1      (enabled)
2:  HDMI1    
3:  DP1      

$ mons -D 3
$ mons
Monitors: 3
Mode: duplicate
0:  eDP1      (enabled)
2:  HDMI1    
3:  DP1       (enabled)

$ mons -D 2,3
$ mons
Monitors: 3
Mode: duplicate
0:  eDP1      (enabled)
2:  HDMI1     (enabled)
3:  DP1       (enabled)

Same logical with -M option.