list-different (and check) log every file in CI, instead of just changed files

Environments:

• Prettier Version: 1.16.1
• Running Prettier via: CLI
• Runtime: Node.js 10 (and probably every version)
• Operating System: Linux

Steps to reproduce:

• Use this reproduction repo and specifically this PR for an illustration of the issue

Expected behavior:

prettier --list-different (and prettier --check) should only log the different files in CI

Actual behavior:

prettier --list-different logs every file in a CI server, tested with TravisCI and CircleCI.

More information

Prettier v1.16.1 tweaked the behavior of --list-different (and additionally --check). It appears to now log all files that are being checked, rather than just the files that differ. In a local, non-CI environment this works well because the shell is wiped with each new file, and the end result ends up being just the files that are changed. In CI, this behavior is not present, and so the output becomes incredibly challenging to read and it’s not clear which files are different and should be updated.

It appears that this PR may have been the cause of the regression, specifically with relying on only process.stdout.isTTY which seems to log every file being accessed in CI.

[SimenB]

Or https://github.com/watson/is-ci

It supports azure pipelines as well (https://github.com/watson/ci-info/pull/23)

[DSchau]

It has been! Working great for us on Gatsby!

Thank you!!