Use link in UI which returned a relative url but not html_url which contains an absolute url (#21986)

partially fix #19345

This PR add some `Link` methods for different objects. The `Link`
methods are not different from `HTMLURL`, they are lack of the absolute
URL. And most of UI `HTMLURL` have been replaced to `Link` so that users
can visit them from a different domain or IP.

This PR also introduces a new javascript configuration
`window.config.reqAppUrl` which is different from `appUrl` which is
still an absolute url but the domain has been replaced to the current
requested domain.

routers/web/feed/convert.go

@@ -73,7 +73,7 @@ func feedActionsToFeedItems(ctx *context.Context, actions activities_model.Actio
 
 		var content, desc, title string
 
-		link := &feeds.Link{Href: act.GetCommentLink()}
+		link := &feeds.Link{Href: act.GetCommentHTMLURL()}
 
 		// title
 		title = act.ActUser.DisplayName() + " "

routers/web/repo/pull.go

@@ -339,8 +339,8 @@ func setMergeTarget(ctx *context.Context, pull *issues_model.PullRequest) {
 		ctx.Data["HeadTarget"] = pull.MustHeadUserName(ctx) + "/" + pull.HeadRepo.Name + ":" + pull.HeadBranch
 	}
 	ctx.Data["BaseTarget"] = pull.BaseBranch
-	ctx.Data["HeadBranchHTMLURL"] = pull.GetHeadBranchHTMLURL()
-	ctx.Data["BaseBranchHTMLURL"] = pull.GetBaseBranchHTMLURL()
+	ctx.Data["HeadBranchLink"] = pull.GetHeadBranchLink()
+	ctx.Data["BaseBranchLink"] = pull.GetBaseBranchLink()
 }
 
 // PrepareMergedViewPullInfo show meta information for a merged pull request view page

routers/web/repo/repo.go

@@ -569,6 +569,7 @@ func SearchRepo(ctx *context.Context) {
 			Mirror:   repo.IsMirror,
 			Stars:    repo.NumStars,
 			HTMLURL:  repo.HTMLURL(),
+			Link:     repo.Link(),
 			Internal: !repo.IsPrivate && repo.Owner.Visibility == api.VisibleTypePrivate,
 		}
 	}