Validate on `shopify theme share/pull/push/serve` if users are running the command in a theme/empty directory

[Poitrin]

WHY are these changes introduced?

• Fixes #2669
• Fixes #2623
• CLI 3.x related PR: https://github.com/Shopify/cli/pull/751

We want to…

• ensure that partners execute shopify theme share/pull/push/serve/dev in the correct directory
• enforce the usage of the theme architecture directory structure

WHAT is this pull request doing?

Requests a confirmation from the user to the following question …

It doesn’t seem like you’re running this command in a theme directory. Are you sure you want to proceed?

… if users …

• try running shopify theme share in a directory that doesn't seem [1] like a theme directory
• try running shopify theme serve/dev in a directory that doesn't seem [1] like a theme directory
• try running shopify theme push in a directory that doesn't seem [1] like a theme directory
• try running shopify theme pull in a directory that doesn't seem [1] like a theme directory or it's not empty

[1] https://shopify.dev/themes/architecture#directory-structure-and-component-types

How to test your changes?

No confirmation needed

Part 1:

• cd into a directory that seems like a theme directory and contains some theme files.
• Run shopify theme share/serve/push
• Are the commands running without any confirmation?

Part 2:

• cd into an empty directory, or a directory with at least the folders %w(config layout sections templates)
• Run shopify theme pull
• Is the command running without any confirmation?

Confirmation needed

Part 1:

• cd into an empty directory, or a directory that does not contain all the folders %w(config layout sections templates)
• Run shopify theme share/serve/push
• Does the desired confirmation dialogue appear?
• Does the CLI exit when you answer No?
• Does the CLI continue when you answer Yes?

Part 2:

• cd into a non-empty directory that does not contain all the folders %w(config layout sections templates)
• Run shopify theme pull
• Does the desired confirmation dialogue appear?
• Does the CLI exit when you answer No?
• Does the CLI continue when you answer Yes?

Post-release steps

• [x] Update shopify.dev docs, as --force flag has been added. – flag is hidden, so no need to update docs f.t.m.

Update checklist

• [x] I've added a CHANGELOG entry for this PR (if the change is public-facing)
• [x] I've considered possible cross-platform impacts (Mac, Linux, Windows).
• [x] I've left the version number as is (we'll handle incrementing this when releasing).
• [x] I've included any post-release steps in the section above (if needed).

[mgmanzella]

one more thing! i noticed when testing i select no to not proceed and from the CLI 3, the CLI hangs and doesn't exit. I have to ctrl-C to exit the CLI. have you seen this happen? (it could also be my setup so im skeptical there's actually a bug 😅 but thought i'd mention anyway)

[Poitrin]

i noticed when testing i select no to not proceed and from the CLI 3, the CLI hangs and doesn't exit. I have to ctrl-C to exit the CLI. have you seen this happen? (it could also be my setup so im skeptical there's actually a bug 😅 but thought i'd mention anyway)

Thanks for highlighting this! I will take a closer look again and then potentially add changes to https://github.com/Shopify/cli/pull/743 :-)