Allow adding multiple issues to a project (#17226)

Adds an option like for adding multiple issues to a milestone.
Closes #17216

Author: qwerty287

Diff for: routers/web/repo/issue.go

@@ -327,6 +327,20 @@ func issues(ctx *context.Context, milestoneID, projectID int64, isPullOption uti
 		}
 		return 0
 	}
+
+	if ctx.Repo.CanWriteIssuesOrPulls(ctx.Params(":type") == "pulls") {
+		projects, _, err := models.GetProjects(models.ProjectSearchOptions{
+			RepoID:   repo.ID,
+			Type:     models.ProjectTypeRepository,
+			IsClosed: util.OptionalBoolOf(isShowClosed),
+		})
+		if err != nil {
+			ctx.ServerError("GetProjects", err)
+			return
+		}
+		ctx.Data["Projects"] = projects
+	}
+
 	ctx.Data["IssueStats"] = issueStats
 	ctx.Data["SelLabelIDs"] = labelIDs
 	ctx.Data["SelectLabels"] = selectLabels

Diff for: templates/repo/issue/list.tmpl

@@ -166,6 +166,24 @@
 						</div>
 					</div>
 
+					<!-- Projects -->
+					<div class="ui {{if not .Projects}}disabled{{end}} dropdown jump item">
+						<span class="text">
+							{{.i18n.Tr "repo.project_board"}}
+							{{svg "octicon-triangle-down" 14 "dropdown icon"}}
+						</span>
+						<div class="menu">
+							<div class="item issue-action" data-element-id="0" data-url="{{$.Link}}/projects">
+							{{.i18n.Tr "repo.issues.new.no_projects"}}
+							</div>
+							{{range .Projects}}
+								<div class="item issue-action" data-element-id="{{.ID}}" data-url="{{$.RepoLink}}/issues/projects">
+									{{.Title}}
+								</div>
+							{{end}}
+						</div>
+					</div>
+
 					<!-- Assignees -->
 					<div class="ui {{if not .Assignees}}disabled{{end}} dropdown jump item">
 						<span class="text">