[cknitt]

For a pull_request event, GitHub runs the workflow file of the pull request's test merge into master, but the Semantic Diff workflow checked out its scripts from the pull request's head. A branch made before #8958 therefore ran master's workflow, which passes --markdown, --url and --since, against its old commitRecords.js, which read --markdown as a revision:

Error: Command failed: git show -s --format=%h --abbrev=9 --markdown

This failed the latest runs on the #8951 stack (#8950, #8948, #8949).

The checkout now takes github.sha, the merge commit the workflow itself comes from, so the workflow and the scripts always match: master's tooling plus whatever the pull request changes in it. The rendered commits are unchanged, since the renderer reads them through the pr-<N> ref. Fork pull requests (pull_request_target) keep checking out the base branch.

🤖 Generated with Claude Code

https://claude.ai/code/session_01AzPS5F8RDSGZ6dhfK6NdZp

[github-actions]

Semantic Diff

1 commit · Full page

Render the semantic diff with the workflow's own scripts

_{2abf182 · Christoph Knittel with Claude Opus 5.5 · Oct 22, 2026}

A pull request's run takes the workflow from its merge into master but checked out the renderer from the branch, so a branch made before #8958 passed --markdown to a commitRecords.js that took it for a revision. The renderer now comes from the merge as well.

[github-actions]

Semantic Diff

1 commit · Full page

Render the semantic diff with the workflow's own scripts

_{d1edaff · Christoph Knittel with Claude Opus 5.5 · Oct 22, 2026}

A pull request's run takes the workflow from its merge into master but checked out the renderer from the branch, so a branch made before #8958 passed --markdown to a commitRecords.js that took it for a revision. The renderer now comes from the merge as well.

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commit: d1edaff

[github-actions]

Developer playground preview: https://rescript-lang.github.io/rescript/dev-playground/?version=pr-8963