[Fix] Infer PR for watch

[Green-Ranger11]

Removes check for whether PR is specified so that watch can infer PR. Also adds a check so that if sha and pr are not able to be inferred or specified an error is thrown.

This closes #42

[ljharb]

Suggested change

	if (argv.watch && !argv.sha && !argv.pr) {
	throw chalk.red('Could not infer sha. Please specify a pull request to watch with --pr');
	}
	if (argv.watch && !argv.sha && !argv.pr) {
	throw chalk.red('Could not infer a PR or a SHA. Please specify a pull request to watch with `--pr`, or a commit with `--sha`');
	}

[ljharb]

Using this PR, i ran this:

can-merge --remote=source --watch && git push source

on ecma262, on tc39/ecma262#2605. I got a bunch of dots, and then expected it to be completed and push up the changes. However, I got:

PR: 2605 ✔ This PR is mergeable
..........Enumerating objects: 5, done.
Counting objects: 100% (5/5), done.
Delta compression using up to 16 threads
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 1.59 KiB | 1.59 MiB/s, done.
Total 3 (delta 2), reused 0 (delta 0), pack-reused 0
remote: Resolving deltas: 100% (2/2), completed with 2 local objects.
remote: error: GH006: Protected branch update failed for refs/heads/main.
remote: error: Required status check "Begin.com build preview" is expected.
To github.com:tc39/ecma262.git
 ! [remote rejected]   HEAD -> main (protected branch hook declined)
error: failed to push some refs to 'github.com:tc39/ecma262.git'

So it seems like it was missing this required status - possibly because the status is not actually set on the PR until later in the process?

[Green-Ranger11]

Hmmm I am confused though by what you mean by "not set on the PR until later in process"?

[ljharb]

What i mean is, most statuses get set on the PR as “pending” right away. In this case, the deploy preview status is not set at all until after the build status is completed. However, because the repo has it as “required”, it shows up anyways on the PR, but may not show up in the api response.

[Green-Ranger11]

It might be we're not correctly querying GitHub as well in addition to the point you mentioned. I will do some research and get back in addition to fixing the tests.

[ljharb]

I agree it's not specifically related to this PR, since it happens with and without --watch, but I wanted to call it out.

[ljharb]

(This one can land once tests are passing)