[match] prevent directory download from s3

[markhomoki]

Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I see several green ci/circleci builds in the "All checks have passed" section of my PR (connect CircleCI to GitHub if not)
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

Currently, we use match and store our certificates on GitHub. However, we decided to move away from GitHub and store the certificates on s3. There are several iOS apps we maintain. After migrating the certificates to s3 (and following the same format match uses), we faced a problem when match tries to download the root folder instead of the certificates.
Resolves #19363

Description

When match creates the distribution certificate and pushes it to s3, everything works perfectly. However, when uploading the exact files and folder structure to s3, the match script cannot find the certificates the script fails. It happens because in that cases, s3_client.find_bucket!(s3_bucket).objects(prefix: s3_object_prefix) returns the root directory as well, which fails with the following error: No such file or directory @ rb_sysopen. Adding a check to prevent downloading directories, fixes the problem.

Testing Steps

1. Let match create the certificates and upload them to s3
2. Login to s3 where you can access files
3. Make a note of the team name, then rename the folder to something else
4. Change the folder name back to the team name
5. Without this fix, the match script fails

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[mikiest]

Seems very reasonable and low risk.

[markhomoki]

@rogerluan Sorry for tagging you, but I'm curious if this can be merged, or there's anything I need to update. Unfortunately, we are unable to use the latest version of fastlane without this PR.

[rogerluan]

Hi @markhomoki !

Thanks for opening this PR 🙏 Any chance you can add unit tests that cover this case? That way we can ensure this works as expected, and that it won't regress in the future as well

[markhomoki]

Thanks @rogerluan. Sorry for taking this long, but i've updated my PR. Tested the cases locally and they are working. For some reason it fails on Xcode 13.0.0 with Ruby 3.1.. (Also, seen other PRs that have the same issue)

[rogerluan]

Thanks for the heads up @markhomoki , I'll check what's going on 💪

[rogerluan]

This might fix CI, let's see: #21465

[markhomoki]

Thanks @rogerluan , seems like all good

[rogerluan]

💪 Looks good! Thank you for this PR! 🤗