Add guide page to actions when there's no workflows (#28145)

Before:

![image](https://github.com/go-gitea/gitea/assets/18380374/599d40c1-9b8d-4189-9286-c9c36fb780dd)

After:

![image](https://github.com/go-gitea/gitea/assets/18380374/848a73d1-aaec-478f-93a7-adcc7ee18907)

modules/context/repo.go

@@ -563,6 +563,7 @@ func RepoAssignment(ctx *Context) context.CancelFunc {
 	ctx.Data["CanWriteCode"] = ctx.Repo.CanWrite(unit_model.TypeCode)
 	ctx.Data["CanWriteIssues"] = ctx.Repo.CanWrite(unit_model.TypeIssues)
 	ctx.Data["CanWritePulls"] = ctx.Repo.CanWrite(unit_model.TypePullRequests)
+	ctx.Data["CanWriteActions"] = ctx.Repo.CanWrite(unit_model.TypeActions)
 
 	canSignedUserFork, err := repo_module.CanUserForkRepo(ctx, ctx.Doer, ctx.Repo.Repository)
 	if err != nil {

options/locale/locale_en-US.ini

@@ -3529,6 +3529,9 @@ runs.status = Status
 runs.actors_no_select = All actors
 runs.status_no_select = All status
 runs.no_results = No results matched.
+runs.no_workflows = There are no workflows yet.
+runs.no_workflows.quick_start = Don't know how to start with Gitea Action? See <a target="_blank" rel="noopener noreferrer" href="%s">the quick start guide</a>.
+runs.no_workflows.documentation = For more information on the Gitea Action, see <a target="_blank" rel="noopener noreferrer" href="%s">the documentation</a>.
 runs.no_runs = The workflow has no runs yet.
 runs.empty_commit_message = (empty commit message)
 

templates/repo/actions/list.tmpl

@@ -4,6 +4,7 @@
 	<div class="ui container">
 		{{template "base/alert" .}}
 
+		{{if .workflows}}
 		<div class="ui stackable grid">
 			<div class="four wide column">
 				<div class="ui fluid vertical menu">
@@ -78,6 +79,9 @@
 				{{template "repo/actions/runs_list" .}}
 			</div>
 		</div>
+		{{else}}
+			{{template "repo/actions/no_workflows" .}}
+		{{end}}
 	</div>
 </div>
 {{template "base/footer" .}}

templates/repo/actions/no_workflows.tmpl

@@ -0,0 +1,8 @@
+<div class="empty-placeholder">
+	{{svg "octicon-no-entry" 48}}
+	<h2>{{ctx.Locale.Tr "actions.runs.no_workflows"}}</h2>
+	{{if and .CanWriteCode .CanWriteActions}}
+		<p>{{ctx.Locale.Tr "actions.runs.no_workflows.quick_start" "https://docs.gitea.com/usage/actions/quickstart/" | Safe}}</p>
+	{{end}}
+	<p>{{ctx.Locale.Tr "actions.runs.no_workflows.documentation" "https://docs.gitea.com/usage/actions/overview/" | Safe}}</p>
+</div>