feat(behaviors): &key_repeat behavior + tests.

[petejohanson]

• Add new &key_repeat behavior that captures and re-sends
  the most recently triggered keycode.

[petejohanson]

Closes #853

[dxmh]

Nice @petejohanson!

I have noticed that it doesn't currently repeat keys with modifiers applied:

• alt+left will only repeat left
• cmd+space will only repeat space
• shift+t will only repeat a lowercase t, etc.

However, it does repeat modified keys when modifier functions are used:

• tap &kp LG(V) and it will repeat cmd+v (paste)
• hold &kp LGUI, tap &kp V and it will only repeat v
• tap &sk LGUI, tap &kp V and it will only repeat v

Is this intentional with the current implementation? My initial expectation was that all three of the above scenarios would repeat cmd+v (paste).

[jcmkk3]

Nice @petejohanson!

I have noticed that it doesn't currently repeat keys with modifiers applied:

• alt+left will only repeat left
• cmd+space will only repeat space
• shift+t will only repeat a lowercase t, etc.

However, it does repeat modified keys when modifier functions are used:

• tap &kp LG(V) and it will repeat cmd+v (paste)
• hold &kp LGUI, tap &kp V and it will only repeat v
• tap &sk LGUI, tap &kp V and it will only repeat v

Is this intentional with the current implementation? My initial expectation was that all three of the above scenarios would repeat cmd+v (paste).

This is a good callout. I was wondering if it would be applied this way or not. One of the reasons that it has always been desirable is to help repeating some mod-based shortcuts that can be a pain to repeat using callum-style mods or at the very least require planning to know that you're going to repeat it. ctrl-d for multiple cursors or ctrl-s for progressing to the next search candidate in emacs are examples of where I could see using it. I will probably start by putting it on my nav layer, but may later try to incorporate it into the alphas somehow.

[petejohanson]

@dxmh @jcmkk3 Please pull the latest and try again. Added code to capture the current mods, along w/ corresponding test case.