<!--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=591440) </details> <!--IssueSummary end--> ### Summary After upgrading from 18.8.4.-ce.0 to 18.9.0-ce.0, notification emails generated by the "email on push" integration have stopped including diffs for text files larger than 512 KB, instead showing "No preview for this file type". This is independent of the size of the diff and only depends on the size of the file after the commit. Files up to 524288 Bytes = 2**19 Bytes = 512 KB work fine. The diff renders fine in the Web UI, but is not included in the notification email. The issue is reproducible on gitlab.com with this test repository: https://gitlab.com/lweberefn1/test-email-on-push ### Steps to reproduce 1. Create new repository (or use below test repository) 2. Enable "Email on push" integration 3. Create a file larger than 512 KB (for example, by running the python script in the test repository as `python3 gen-files.py 524289`) 4. git add, git commit, git push 5. Introduce a change in this file, keeping the file size at or above 524288 Bytes (a small change is enough) 6. Commit and push 7. Observe the notification email showing "No preview for this file type" ### Example Project Example project: https://gitlab.com/lweberefn1/test-email-on-push Example commit: https://gitlab.com/lweberefn1/test-email-on-push/-/commit/84db76b0b2d297cc9fa5cdfd8470e90a272e26dd ### What is the current _bug_ behavior? For text files larger than 512 KB, "No preview for this file type" is shown instead of the diff. ### What is the expected _correct_ behavior? The diff should be shown (unless the diff itself is too large, which would be indicated by the message "The diff for this file was not included because it is too large."). ### Relevant logs and/or screenshots {width=547 height=600} ### Output of checks This bug happens on GitLab.com ### Possible fixes The issue seems to be similar to https://gitlab.com/gitlab-org/gitlab/-/issues/20838 but with a much lower file size limit. I’ve verified that also in this case, the problem is that `blob.readable_text?` (https://gitlab.com/gitlab-org/gitlab-foss/-/blob/master/app/models/blob.rb#L216) is false due to `truncated?` being true, although I was unable to find es the exact problem leading to the 512 KB limit. <!--If you don't have /label privileges, follow up with an issue comment of `@gitlab-bot label ~"type::bug"`-->