ci: read the commit message from env in the doc-only check - #1170

Hi, and thanks for PDFMathTranslate.

In .github/workflows/python-publish.yml, the "Check if commit is doc-only" step reads the commit message by interpolation:

run: |
  MSG=$(echo "${{ github.event.head_commit.message }}" | head -n 1)
  if [[ "$MSG" == doc:* ]] || [[ "$MSG" == "doc("* ]]; then

Actions expands ${{ ... }} into the script text before bash runs, so the commit message becomes part of the command rather than input to echo. A commit message is free text — it comes in with whatever a contributor wrote in the PR they got merged — and $(...) and backticks still run inside double quotes.

This is the "Test and Release" workflow, which is why I thought it worth raising rather than leaving be. It is on: push to main/master, so a message only gets here after someone merged it, and the reviewer is looking at the diff rather than the commit text.

The change reads the message from the environment:

env:
  COMMIT_MESSAGE: ${{ github.event.head_commit.message }}
run: |
  MSG=$(printf '%s' "$COMMIT_MESSAGE" | head -n 1)

I used printf '%s' rather than echo so a message beginning with something like -n is not treated as a flag; the head -n 1 and both doc: / doc( prefix tests are unchanged, so doc-only detection behaves exactly as before.

The same line appears in fork-test.yml. I have kept this PR to python-publish.yml so it stays easy to review, and I am happy to send the same change for the other one if you would like it.

Disclosure: I used AI assistance to help spot this and prepare the change, and I read both workflows myself.