Add "Update Branch" button to Pull Requests (#9784)

* add Divergence

* add Update Button

* first working version

* re-use code

* split raw merge commands and db-change functions (notify, cache, ...)

* use rawMerge (remove redundant code)

* own function to get Diverging of PRs

* use FlashError

* correct Error Msg

* hook is triggerd ... so remove comment

* add "branch2" to "user2/repo1" because it unit-test "TestPullView_ReviewerMissed" use it but dont exist jet :/

* move GetPerm to IsUserAllowedToUpdate

* add Flash Success MSG

* imprufe code
- remove useless js chage

* fix-lint

* TEST: add PullRequest ID:5
Repo: user2/repo1
Base: branch1
Head: pr-to-update

* correct comments

* make PR5 outdated

* fix Tests

* WIP: add pull update test

* update revs

* update locales

* working TEST

* update UI

* misspell

* change style

* add 1s delay so rev exist

* move row up (before merge row)

* fix lint nit

* UI remove divider

* Update style

* nits

* do it right

* introduce IsSameRepo

* remove useless check

Co-authored-by: Lauris BH <lauris@nix.lv>

templates/repo/issue/view_content/pull.tmpl

@@ -157,6 +157,26 @@
 							{{$.i18n.Tr (printf "repo.signing.wont_sign.%s" .WontSignReason) }}
 						</div>
 					{{end}}
+					{{if and .Divergence (gt .Divergence.Behind 0)}}
+					<div class="ui very compact branch-update grid">
+  						<div class="row">
+							<div class="item text gray eleven wide left floated column">
+								<i class="icon icon-octicon"><span class="octicon octicon-alert"></span></i>
+								{{$.i18n.Tr "repo.pulls.outdated_with_base_branch"}}
+							</div>
+							{{if .UpdateAllowed}}
+								<div class="item text five wide right floated column">
+									<form action="{{.Link}}/update" method="post">
+										{{.CsrfTokenHtml}}
+										<button class="ui button" data-do="update">
+											<span class="item text">{{$.i18n.Tr "repo.pulls.update_branch"}}</span>
+										</button>
+									</form>
+								</div>
+							{{end}}
+						</div>
+					</div>
+					{{end}}
 					{{if .AllowMerge}}
 						{{$prUnit := .Repository.MustGetUnit $.UnitTypePullRequests}}
 						{{$approvers := .Issue.PullRequest.GetApprovers}}