RSS/Atom support for Repos (#19055)

* support for repos
* refactor
* advertise the feeds via meta tags
* allow feed suffix and feed header
* optimize performance

modules/context/repo.go

@@ -418,6 +418,8 @@ func RepoAssignment(ctx *Context) (cancel context.CancelFunc) {
 	userName := ctx.Params(":username")
 	repoName := ctx.Params(":reponame")
 	repoName = strings.TrimSuffix(repoName, ".git")
+	repoName = strings.TrimSuffix(repoName, ".rss")
+	repoName = strings.TrimSuffix(repoName, ".atom")
 
 	// Check if the user is the same as the repository owner
 	if ctx.IsSigned && ctx.User.LowerName == strings.ToLower(userName) {