ci: prevent merge by commit message

[burgerdev]

In addition to the do-not-merge label, this prevents merging commits that start their subject with one of the following phrases:

• DO NOT MERGE
• DNM
• draft

---

Example failure: https://github.com/edgelesssys/contrast/actions/runs/18350842068/job/52270109970?pr=1830

[charludo]

should probably be renamed to prevent_accidental_merge.yml or similar

[charludo]

Suggested change

	if ! git log --pretty=format:"%s" "${BASE_SHA}..${HEAD_SHA}" | grep -E "^(DNM|DO NOT MERGE|draft)"; then
	if ! git log --pretty=format:"%s" "${BASE_SHA}..${HEAD_SHA}" | grep -iE "^(dnm|do not merge|draft|temp)"; then

(i flag for robustness, temp for... personal reasons, feel free to ignore 😆)

[katexochen]

In addition to the do-not-merge label, this prevents merging commits that start their subject with one of the following phrases:

Did that happen before?

• DO NOT MERGE
• DNM
• draft

usually such labels would at least go into [ ], I would add [no ci]. But to be honest, I think we could spend hours finding things people mark the wip commits with, and I don't see a lot of value here.

[burgerdev]

In addition to the do-not-merge label, this prevents merging commits that start their subject with one of the following phrases:

Did that happen before?

I use DO NOT MERGE as a prefix, and I saw others use that, too. Whenever I see it in review, I feel the need to comment "make sure to drop this", but I'd rather have a robot think of it.

• DO NOT MERGE
• DNM
• draft

usually such labels would at least go into [ ], I would add [no ci]. But to be honest, I think we could spend hours finding things people mark the wip commits with, and I don't see a lot of value here.

I can relax the regex a bit.