Note the SHA at the top of my build:

But this is the output from the end of actions/checkout:
HEAD is now at c28ff3a5b fix: Use React 16.9.0.
Removed matchers: 'checkout-git'
##[remove-matcher owner=checkout-git]
It seems to be checking out the latest master, instead of the branch I'm actually on. This was working on Saturday.
Actually, I think perhaps something more fundamental is broken here:
- run: 'echo Sha is: $SHA'
env:
SHA: ${{ github.sha }}
results in:
Sha is:
Where's my sha? O_o
The default $GITHUB_SHA is also empty.
Even the ref is missing! Running cmd /c "set" on Windows gives:
[...]
GITHUB_BASE_REF=
GITHUB_EVENT_NAME=push
GITHUB_EVENT_PATH=d:\a\_temp\_github_workflow\event.json
GITHUB_HEAD_REF=
GITHUB_REF=
GITHUB_REPOSITORY=nulano/Pillow
GITHUB_SHA=
[...]
This broke about an hour ago.
@nulano I beat you to it by a minute, I'm afraid: https://github.community/t5/GitHub-Actions/PSA-GitHub-Actions-are-a-bit-broken-this-morning-missing-SHAs/m-p/33282#M1438 ;)
ACK
We have deployed a fix for this. Sorry! 馃槗 @jwalton how is it looking for you?
Looks OK for me now.
@timruffles Working for me now! Don't worry, you're still beta, you can break stuff. ;) Thanks for the quick fix!
Most helpful comment
We have deployed a fix for this. Sorry! 馃槗 @jwalton how is it looking for you?