If the temporary branch we want to push to is protected by a wildcard,
we need to add a temporary protected branch entry to allow the current
user to push to it, even if they can't administer the project.

In this case, we can save a lot of time and gymnastics by just
immediately returning the commit SHA. If it can't be merged, the
squashed commit couldn't be merged either.

* 'Learn more' should be 'about this feature'
* The feature is to squash and merge at once, not squash before merge

1. Clone the repo to a temp directory.
2. Apply the MR as a patch.
3. Use `git commit -C` to copy the commit metadata from the HEAD commit
   of the source branch, and manually add the merging user as the
   committer.
4. Push back to a randomly-generated branch name.
5. Immediately delete that branch, so that it does not appear in the
   branch list, trigger CI builds, etc.
6. Return the SHA of the squashed commit we've just pushed to the
   MergeService.
7. In the MergeService, allow an arbitrary source to be used, and set
   that to either the source branch (if there is no squashing) or the
   squashed SHA.

When squashing, we may want to merge a different commit than the MR's
HEAD commit into the target branch. This interface matches the existing
`Repository#ff_merge` method, and allows us to pick an arbitrary commit
to merge.

Update the 8.16.3 changelog in master

See merge request !1145

Ignore encrypted attributes in Import/Export (EE version)

See merge request !1140

Closes #24458

See merge request !8739
# Conflicts:
#	spec/features/projects/import_export/test_project_export.tar.gz

CE upstream

See merge request !1139

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

UX Guide: minor updates

See merge request !8862

[ci skip] UX guide: clean up term tables in copy

[ci skip] UX guide: update dropdown max height for multiline items

Remove hard-coded absolute URLs from all frontend assets

See merge request !8831

Fixed Issuable sidebar so it remains closed on mobile/smaller screen devices

See merge request !7466

[ci skip]

[ci skip]

Merge branch '27248-filtered-search-does-not-allow-filtering-labels-with-multiple-words' into 'master'

Fix filtering label and milestone with multiple words

Closes #27248 and #27334

See merge request !8830

[EE] Resolve "NameError: uninitialized constant ApplicationSetting::DEFAULTS"

See merge request !1124

Resolve "NameError: uninitialized constant ApplicationSetting::DEFAULTS"

Closes #27280

See merge request !8805

Merge branch '26448-unnecessary-request-is-made-when-filter-input-box-is-focused-by-keyboard' into 'master'

Only search commits on input change since last search

Closes #26448

See merge request !8488