Disable merging a WIP Pull request (#4529)

* prevent pull request to be merged when PR is a WIP

* add tests

* add helper to prepend WIP: in PR title

* move default wip prefixes into settings

* use configurable WIP prefixes in javascript and default to first one in templates

* add documentation

* add unit test on pull model

Signed-off-by: Julien Tant <julien@craftyx.fr>

templates/repo/issue/view_content/pull.tmpl

@@ -2,6 +2,7 @@
 	<a class="avatar text
 	{{if .Issue.PullRequest.HasMerged}}purple
 	{{else if .Issue.IsClosed}}grey
+	{{else if .IsPullWorkInProgress}}grey
 	{{else if .IsPullRequestBroken}}red
 	{{else if .Issue.PullRequest.IsChecking}}yellow
 	{{else if .Issue.PullRequest.CanAutoMerge}}green
@@ -27,6 +28,11 @@
 					<span class="octicon octicon-x"></span>
 					{{$.i18n.Tr "repo.pulls.data_broken"}}
 				</div>
+			{{else if .IsPullWorkInProgress}}
+				<div class="item text grey">
+					<span class="octicon octicon-x"></span>
+					{{$.i18n.Tr "repo.pulls.cannot_merge_work_in_progress" .WorkInProgressPrefix | Str2html}}
+				</div>
 			{{else if .Issue.PullRequest.IsChecking}}
 				<div class="item text yellow">
 					<span class="octicon octicon-sync"></span>