Add Feed for Releases and Tags (#21696)

Fixes #19091

Add Feed for Releases and Tags, can be accessed through
`reponame/releases.rss`, `reponame/releases.atom`, `reponame/tags.rss`,
and `reponame/tags.atom`

Signed-off-by: Reo <reo_999@proton.me>

routers/web/feed/convert.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 
 	activities_model "code.gitea.io/gitea/models/activities"
+	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/modules/context"
 	"code.gitea.io/gitea/modules/markup"
 	"code.gitea.io/gitea/modules/markup/markdown"
@@ -268,3 +269,46 @@ func GetFeedType(name string, req *http.Request) (bool, string, string) {
 
 	return false, name, ""
 }
+
+// feedActionsToFeedItems convert gitea's Repo's Releases to feeds Item
+func releasesToFeedItems(ctx *context.Context, releases []*repo_model.Release, isReleasesOnly bool) (items []*feeds.Item, err error) {
+	for _, rel := range releases {
+		err := rel.LoadAttributes(ctx)
+		if err != nil {
+			return nil, err
+		}
+
+		var title, content string
+
+		if rel.IsTag {
+			title = rel.TagName
+		} else {
+			title = rel.Title
+		}
+
+		link := &feeds.Link{Href: rel.HTMLURL()}
+		content, err = markdown.RenderString(&markup.RenderContext{
+			Ctx:       ctx,
+			URLPrefix: rel.Repo.Link(),
+			Metas:     rel.Repo.ComposeMetas(),
+		}, rel.Note)
+
+		if err != nil {
+			return nil, err
+		}
+
+		items = append(items, &feeds.Item{
+			Title:   title,
+			Link:    link,
+			Created: rel.CreatedUnix.AsTime(),
+			Author: &feeds.Author{
+				Name:  rel.Publisher.DisplayName(),
+				Email: rel.Publisher.GetEmail(),
+			},
+			Id:      fmt.Sprintf("%v: %v", strconv.FormatInt(rel.ID, 10), link.Href),
+			Content: content,
+		})
+	}
+
+	return items, err
+}

routers/web/feed/release.go

@@ -0,0 +1,50 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package feed
+
+import (
+	"time"
+
+	repo_model "code.gitea.io/gitea/models/repo"
+	"code.gitea.io/gitea/modules/context"
+
+	"github.com/gorilla/feeds"
+)
+
+// shows tags and/or releases on the repo as RSS / Atom feed
+func ShowReleaseFeed(ctx *context.Context, repo *repo_model.Repository, isReleasesOnly bool, formatType string) {
+	releases, err := repo_model.GetReleasesByRepoID(ctx, ctx.Repo.Repository.ID, repo_model.FindReleasesOptions{
+		IncludeTags: !isReleasesOnly,
+	})
+	if err != nil {
+		ctx.ServerError("GetReleasesByRepoID", err)
+		return
+	}
+
+	var title string
+	var link *feeds.Link
+
+	if isReleasesOnly {
+		title = ctx.Tr("repo.release.releases_for", repo.FullName())
+		link = &feeds.Link{Href: repo.HTMLURL() + "/release"}
+	} else {
+		title = ctx.Tr("repo.release.tags_for", repo.FullName())
+		link = &feeds.Link{Href: repo.HTMLURL() + "/tags"}
+	}
+
+	feed := &feeds.Feed{
+		Title:       title,
+		Link:        link,
+		Description: repo.Description,
+		Created:     time.Now(),
+	}
+
+	feed.Items, err = releasesToFeedItems(ctx, releases, isReleasesOnly)
+	if err != nil {
+		ctx.ServerError("releasesToFeedItems", err)
+		return
+	}
+
+	writeFeed(ctx, feed, formatType)
+}