That's the sort of hook you should be able to write yourself pretty quickly. So I threw your comment into o3-mini-high and it gave me a decent-looking solution. Decent but wrong, since it thought "current git commit" referred to the project repo, rather than the referenced dependency.

Anyway here's the gist of a solution without any of the necessary checking that the files actually exist etc.

  #!/bin/sh
  for file in .github/workflows/*.yml; do
    grep -E "uses:[[:space:]]+[A-Za-z0-9._-]+/[A-Za-z0-9._-]+@v[0-9]+" "$file" | while read -r line; do
      repo=$(echo "$line" | sed -E 's/.*uses:[[:space:]]+([A-Za-z0-9._-]+\/[A-Za-z0-9._-]+)@v[0-9]+.*/\1/')
      tag=$(echo "$line" | sed -E 's/.*@((v[0-9]+)).*/\1/')
      commit_hash=$(git ls-remote "https://github.com/$repo.git" "refs/tags/$tag" | awk '{print $1}')
      [ -n "$commit_hash" ] && sed -i.bak -E "s|(uses:[[:space:]]+$repo@)$tag|\1$commit_hash|g" "$file" && git add "$file" && rm -f "$file.bak"
    done
  done
  exit 0

Thanks! Today I learned:

$ git ls-remote "https://github.com/$repo.git" "refs/tags/$tag"

Even though the grep and sed are not very readable this was very useful way to avoid yet another tool!