Improve counsel-M-x-transformer key lookup

[basil-conto]

Issue

counsel-M-x-transformer unconditionally replaces C-x6 with F2 in the key description, without checking that the latter is still a valid binding.

Recipe

1. make plain

2. (global-set-key [f2] #'ignore)

3. C-j
4. M-x2C-command
   • Expected annotation: C-x6
     
   • Actual annotation: F2
     

Performance

Compared to the incumbent counsel-M-x-transformer, the final version in this PR is up to twice as fast and never slower, regardless of C-x6 replacement. The key-description -> kbd round trip, by contrast, is up to twice as slow as the incumbent. I think this justifies the only slight increase in algorithmic complexity.

[basil-conto]

Compared to the incumbent counsel-M-x-transformer, the final version in this PR is up to twice as fast and never slower, regardless of C-x6 replacement. The key-description -> kbd round trip, by contrast, is up to twice as slow as the incumbent. I think this justifies the only slight increase in algorithmic complexity.

Of course, an even simpler approach would be to get rid of the C-x6 replacement, but I assume you still want that. :)

[abo-abo]

I assume you still want that. :)

Correctly assumed:)

[abo-abo]

Thanks.