Disable "Comment" button when there is no text in gist.github.com #4550

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You can comment on any gist, here is one: https://gist.github.com/tterb/982ae14a9307b80117dbf49f624ce0e8.

When trying to comment and the comment is blank, the comment button is not marked as disabled. However, in the main GitHub UI, the "Comment" button is disabled when the comment is blank.

Current:

Desired:

Here is the steps:

• Add disabled attribute
• Add disabled class
• Set the aria-disabled property to true