<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=294257) </details> <!--IssueSummary end--> Main issue: https://gitlab.com/gitlab-org/gitlab/-/issues/21686 ### Problem After https://gitlab.com/gitlab-org/gitlab/-/issues/21686 was done, we'll start displaying a link to the original merge request for [squash and merge](https://docs.gitlab.com/ee/user/project/merge_requests/versions.html#find-the-merge-request-that-introduced-a-change) commits. However, it will work only for future merge requests. Squashed commits and/ MRs before 2021-01-11 11:07 UTC on ~"gitlab.com" or upgrading GitLab to %13.8 or later on ~"self-managed")) do not show the related MR(s) for it even after !49968 !50178. We want to backfill `squash_commit_sha` for already merged merge requests.  In the following MRs in [www-gitlab-com](https://gitlab.com/gitlab-com/www-gitlab-com) as well as many MRs in gitlab-org/gitlab still do not show related MRs: 1. https://gitlab.com/gitlab-com/www-gitlab-com/-/commit/a4b4ae462c10af79ea1bd1d3181d4aa32e2007eb - shows `No related merge requests found` - `!7218` is shown as related MR 2. https://gitlab.com/gitlab-com/www-gitlab-com/-/commit/8de75fcb4df755e749c0524e3d457ad89734f51f - shows `No related merge requests found` - `!15502` is shown as related MR #### Note A workaround for this has exists before/after gitlab-foss!13713 (gitlab-foss#2383) (%10.5) with Git and third-party tools. !1024 (#150) (%8.17) introduced this feature. cf. #21686 (dup #211608) (%13.8) ### Proposal We need to investigate and find a way to fetch squash commit sha and connect it to the correct merge request. As one of the option, we can try to get the last parent of the merge commit. ```ruby if merge_request.squash? squash_commit_sha = merge_request.merge_commit.parents.last end ``` However, I expect possible edge cases with this approach. 0