Teach GitLab not only to merge changes from a merge-request, but also to
apply patches posted to merge-request in a way like `git am` would do -
without merge commit and directly on top of current branch. Which way to
go is selected by user in web UI, and apply patches is the first option.

There are 3 cases:

- only 1 commit is present in MR -> the only available option is to
  apply that single commit as one patch without a merge

  ( There is no need for merge commit in this case at all: information
    about user who applied the patch goes to "Committer" field in resultant
    commit. Avoiding 1 merge per 1 patch results in cleaner history )

  It is also possible to review patch description directly in web UI,
  before doing the actual application, and correct / amend it as needed.

- several commits are present in MR:

  * it is possible to apply the patches directly on top of current
    branch. Again information about who applied what goes to "Committer"
    field.

  * it is possible to merge MR changes with making a merge commit.

    This variant is useful, when patches from a MR do several logical
    steps to reach one goal, and MR description contain cover letter for
    whole patch series.

    in this case original commits stay untouched and resulting merge
    will contain MR author as author, user who accepted MR as committer,
    and cover letter as merge commit message.

    NOTE we avoid useless "Merge branch X into Y" in merge message, and
        just put MR title into merge subject and MR description into merge
        description.

        This way it is more logical with more important information in
        merge subject and thus e.g. more handy to oversee what a merge brings,
        just by it subject, e.g. via looking at updates via

            gitk --first-parent ...

        or via web.

NOTE for pre-generated references to merge-request we now use full MR
    URL, instead of !<MR-n>. Full URLs work everywhere, not only on
    original site where MR was created, or even only in original repo
    and not its fork on the same site.

TODO detect whether request comes from China and only then show ICP (?).

We show in small font size the same info that is shown on sign_in page:

    "GitLab Nexedi Edition", "About GitLab" and "About Nexedi"

This is good to have and hereby-introduced about-footer area will be
also used in the next patch for ICP too.

XXX placement of .about-footer to be near bottom is done not very
correctly.

Like Omnibus, SlapOS version does not have init script - nothing to
check here.

This is handy for monitoring tools, which could e.g. periodically call check
tasks and instead of parsing output, rely on exit code.

The way we detect if something failed is via hooking into String#red, and if
anything was ever printed in red - that's an error.

The default was switched to HTTP in the previous patch, but let's completely
remove SSH option - we support only HTTP for git fetch/push.

Both fetch and push are possible over https, which is selected by http if
gitlab was configured to use https in external url.

This way to reduce security vectors and possible ways to interact with gitlab
we use https only without ssh at all.

= GitLab Community Edition + Nexedi patches

[ci skip]

Ensures that OAuth/LDAP/SAML users don't need to be confirmed

See merge request !10925

Skip issuable without a project in IssuableExtractor#extract

Closes #31280

See merge request !10906

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Add sub-nav for Project Integration Services edit page

Closes #31174

See merge request !10813

Fix usage ping docs link from empty cohorts page

See merge request !10907

Fix OAuth, LDAP and SAML SSO when regular sign-ups are disabled

See merge request !10904

Wrap MR content -stable branch

See merge request !10914

Signed-off-by: Rémy Coutable <remy@rymai.me>

Add a transaction around `move_issues_to_ghost_user`

See merge request !10465

Properly expire cache for **all** MRs of a pipeline

Closes #31040

See merge request !10770

Fix missing duration for blocked pipelines

Closes #31264

See merge request !10856

Fix incorrect commit status text on main project page

See merge request !10863

Add index on ci_builds.updated_at

Closes #31251

See merge request !10870

Fix 9.1 Gitaly source update steps

Closes #31288

See merge request !10877

Eliminate N+1 queries in loading namespaces for every issuable in milestones

See merge request !10871

Ensure replying to an individual note by email creates a note with its own discussion ID

Closes #31067

See merge request !10890

Fix email not being sent after project export

Closes #30676

See merge request !10578

[ci skip]

This reverts commit 0385b5b3.

discussions docs

See merge request !10390

Based on !10841 Fix Error 500 when referencing issue with project in pending delete

Closes #31215

See merge request !10843

Mention Microsoft teams service in project services doc

See merge request !10815

Add doc for scheduled trigger

Closes #30440

See merge request !10591

Port of 31189-pipelines-error-state to 9-1-stable

See merge request !10844