Support downloading raw task logs (#24451)

Hi!
This pull request adds support for downloading raw task logs for Gitea
Actions, similar to Github Actions
It looks like the following:

![image](https://user-images.githubusercontent.com/945339/235376746-405d5019-710b-468b-8113-9e82eab8e752.png)

routers/web/repo/actions/view.go

@@ -8,6 +8,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strings"
 	"time"
 
 	actions_model "code.gitea.io/gitea/models/actions"
@@ -310,6 +311,55 @@ func rerunJob(ctx *context_module.Context, job *actions_model.ActionRunJob) erro
 	return nil
 }
 
+func Logs(ctx *context_module.Context) {
+	runIndex := ctx.ParamsInt64("run")
+	jobIndex := ctx.ParamsInt64("job")
+
+	job, _ := getRunJobs(ctx, runIndex, jobIndex)
+	if ctx.Written() {
+		return
+	}
+	if job.TaskID == 0 {
+		ctx.Error(http.StatusNotFound, "job is not started")
+		return
+	}
+
+	err := job.LoadRun(ctx)
+	if err != nil {
+		ctx.Error(http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	task, err := actions_model.GetTaskByID(ctx, job.TaskID)
+	if err != nil {
+		ctx.Error(http.StatusInternalServerError, err.Error())
+		return
+	}
+	if task.LogExpired {
+		ctx.Error(http.StatusNotFound, "logs have been cleaned up")
+		return
+	}
+
+	reader, err := actions.OpenLogs(ctx, task.LogInStorage, task.LogFilename)
+	if err != nil {
+		ctx.Error(http.StatusInternalServerError, err.Error())
+		return
+	}
+	defer reader.Close()
+
+	workflowName := job.Run.WorkflowID
+	if p := strings.Index(workflowName, "."); p > 0 {
+		workflowName = workflowName[0:p]
+	}
+	ctx.ServeContent(reader, &context_module.ServeHeaderOptions{
+		Filename:           fmt.Sprintf("%v-%v-%v.log", workflowName, job.Name, task.ID),
+		ContentLength:      &task.LogSize,
+		ContentType:        "text/plain",
+		ContentTypeCharset: "utf-8",
+		Disposition:        "attachment",
+	})
+}
+
 func Cancel(ctx *context_module.Context) {
 	runIndex := ctx.ParamsInt64("run")
 

routers/web/web.go

@@ -1207,6 +1207,7 @@ func registerRoutes(m *web.Route) {
 						Get(actions.View).
 						Post(web.Bind(actions.ViewRequest{}), actions.ViewPost)
 					m.Post("/rerun", reqRepoActionsWriter, actions.RerunOne)
+					m.Get("/logs", actions.Logs)
 				})
 				m.Post("/cancel", reqRepoActionsWriter, actions.Cancel)
 				m.Post("/approve", reqRepoActionsWriter, actions.Approve)