feat(ssh-keyscan): new completion

[scop]

No description provided.

[akinomyoga]

Thank you for updating the PR. I have tested the new commit and found that the fields before the comma is removed when there are multiple completions for the string after the comma. For example, in the following cases, it works as expected:

$ ssh-keyscan -t rsa,TAB TAB
dsa      ecdsa    ed25519     # <- the list is shown
$ ssh-keyscan -t rsa,dTAB
$ ssh-keyscan -t rsa,dsa     # <- correctly completed

But in the following ambiguous case, the fields before comma is deleted by TAB.

$ ssh-keyscan -t rsa,eTAB
$ ssh-keyscan -t e     # <- "rsa," is lost

[scop]

Seems what you describe happens with set show-all-if-ambiguous off only, I have it set to on and it works as expected for me (Ubuntu 20.04, bash 5.0.17(1)-release). Opened #552 for that, I suggest we don't wait for that here.

[akinomyoga]

OK, fine! I now approve this PR for merging.