The first attempt didn't migrate all rows on GitLab.com, due to a couple of
issues:

1. Some rows in merge_request_diffs had truly huge numbers of commits and diffs
   serialised - one in particular had 26,000 commits!
2. The jobs were sometimes on Sidekiq hosts with frequent OOM errors, leading to
   the job being lost.

The previous commit adds more logging, and a more robust insertion method. This
commit reschedules the jobs, with a generous pause between each.

This version does not use transactions, but individual statements. As we have
unique constraints on the target tables for the inserts, we can just ignore
uniqueness violations there (as long as we always insert the same batch size, in
the same order).

This means the spec now must use truncation, not a transaction, as the
uniqueness violation means that the whole transaction for that spec would be
invalid, which isn't what we'd want. In real-world use, this isn't run in a
transaction anyway.

This commit also wraps unhandled exceptions, for easier finding in Sentry, and
logs with a consistent format, for easier searching.

We were hitting the statement timeout for very large MR diffs. Now we insert at
most 1,000 rows to `merge_request_diff_commits` in a single statement, or 100
rows to `merge_request_diff_files`.

Add index for merge_requests.merge_commit_sha

Closes #38507

See merge request gitlab-org/gitlab-ce!14549

Tweaked the first time contributor tooltip text

See merge request gitlab-org/gitlab-ce!14565

Fix Auto DevOps banner feature flag

Closes #38576

See merge request gitlab-org/gitlab-ce!14576

Fixed breadcrumb title not linking

Closes #38059

See merge request gitlab-org/gitlab-ce!14532

Remove target dd

Closes #38485

See merge request gitlab-org/gitlab-ce!14558

Add active states to nav bar counters

Closes #37335

See merge request gitlab-org/gitlab-ce!14569

Fixes data parameter not being sent in ajax request for jobs log

Closes #38528

See merge request gitlab-org/gitlab-ce!14564

Guidelines for illustrations

See merge request gitlab-org/gitlab-ce!13097

Migrate Gitlab::Git::Repository#add_tag to Gitaly

Closes gitaly#601

See merge request gitlab-org/gitlab-ce!14500

Closes gitaly#601

Migrate Git::Repository#rm_tag to Gitaly

Closes gitaly#562

See merge request gitlab-org/gitlab-ce!14388

Closes gitaly#562

RepoEditor: Prevent extra network call for already opened files.

Closes #38256

See merge request gitlab-org/gitlab-ce!14489

Docs: Feature overview and use cases

Closes #38076

See merge request gitlab-org/gitlab-ce!14538

Docs: crosslink Pages guides

Closes #38427

See merge request gitlab-org/gitlab-ce!14542

Clear merge requests counter cache after merge

Closes gitlab-ee#3573 and #38344

See merge request gitlab-org/gitlab-ce!14563

Hashed storage migration path

Closes gitlab-ee#3118

See merge request gitlab-org/gitlab-ce!14067

Use relative paths for opening and closing issuables

Closes #35822

See merge request gitlab-org/gitlab-ce!14555

Support custom attributes on users

See merge request gitlab-org/gitlab-ce!13038

Removes the text `Handle with care` as it sounds condescending.

Document the usage of the Docker OverlayFS driver for every build

See merge request gitlab-org/gitlab-ce!14478

Before this change, the MR counter in the sidebar would be wrong if an MR had
been merged since the last update, but not opened or closed, as merging did not
trigger a counter cache update.

Changed account confirmation line to e-mail text.

Closes #13637

See merge request gitlab-org/gitlab-ce!14243

Fix spelling of occurred

See merge request gitlab-org/gitlab-ce!14488