Refactor AddParam to AddParamIfExist (#29834)

When read the code: `pager.AddParam(ctx, "search", "search")`, the
question always comes: What is it doing? Where is the value from? Why
"search" / "search" ?

Now it is clear: `pager.AddParamIfExist("search", ctx.Data["search"])`

routers/web/repo/commit.go

@@ -163,8 +163,8 @@ func Graph(ctx *context.Context) {
 	ctx.Data["CommitCount"] = commitsCount
 
 	paginator := context.NewPagination(int(graphCommitsCount), setting.UI.GraphMaxCommitNum, page, 5)
-	paginator.AddParam(ctx, "mode", "Mode")
-	paginator.AddParam(ctx, "hide-pr-refs", "HidePRRefs")
+	paginator.AddParamIfExist("mode", ctx.Data["Mode"])
+	paginator.AddParamIfExist("hide-pr-refs", ctx.Data["HidePRRefs"])
 	for _, branch := range branches {
 		paginator.AddParamString("branch", branch)
 	}

routers/web/repo/issue.go

@@ -472,16 +472,16 @@ func issues(ctx *context.Context, milestoneID, projectID int64, isPullOption opt
 	}
 	ctx.Data["ShowArchivedLabels"] = archived
 
-	pager.AddParam(ctx, "q", "Keyword")
-	pager.AddParam(ctx, "type", "ViewType")
-	pager.AddParam(ctx, "sort", "SortType")
-	pager.AddParam(ctx, "state", "State")
-	pager.AddParam(ctx, "labels", "SelectLabels")
-	pager.AddParam(ctx, "milestone", "MilestoneID")
-	pager.AddParam(ctx, "project", "ProjectID")
-	pager.AddParam(ctx, "assignee", "AssigneeID")
-	pager.AddParam(ctx, "poster", "PosterID")
-	pager.AddParam(ctx, "archived", "ShowArchivedLabels")
+	pager.AddParamIfExist("q", ctx.Data["Keyword"])
+	pager.AddParamIfExist("type", ctx.Data["ViewType"])
+	pager.AddParamIfExist("sort", ctx.Data["SortType"])
+	pager.AddParamIfExist("state", ctx.Data["State"])
+	pager.AddParamIfExist("labels", ctx.Data["SelectLabels"])
+	pager.AddParamIfExist("milestone", ctx.Data["MilestoneID"])
+	pager.AddParamIfExist("project", ctx.Data["ProjectID"])
+	pager.AddParamIfExist("assignee", ctx.Data["AssigneeID"])
+	pager.AddParamIfExist("poster", ctx.Data["PosterID"])
+	pager.AddParamIfExist("archived", ctx.Data["ShowArchivedLabels"])
 
 	ctx.Data["Page"] = pager
 }

routers/web/repo/milestone.go

@@ -106,8 +106,8 @@ func Milestones(ctx *context.Context) {
 	ctx.Data["IsShowClosed"] = isShowClosed
 
 	pager := context.NewPagination(int(total), setting.UI.IssuePagingNum, page, 5)
-	pager.AddParam(ctx, "state", "State")
-	pager.AddParam(ctx, "q", "Keyword")
+	pager.AddParamIfExist("state", ctx.Data["State"])
+	pager.AddParamIfExist("q", ctx.Data["Keyword"])
 	ctx.Data["Page"] = pager
 
 	ctx.HTML(http.StatusOK, tplMilestone)

routers/web/repo/packages.go

@@ -70,8 +70,8 @@ func Packages(ctx *context.Context) {
 	ctx.Data["RepositoryAccessMap"] = map[int64]bool{ctx.Repo.Repository.ID: true} // There is only the current repository
 
 	pager := context.NewPagination(int(total), setting.UI.PackagesPagingNum, page, 5)
-	pager.AddParam(ctx, "q", "Query")
-	pager.AddParam(ctx, "type", "PackageType")
+	pager.AddParamIfExist("q", ctx.Data["Query"])
+	pager.AddParamIfExist("type", ctx.Data["PackageType"])
 	ctx.Data["Page"] = pager
 
 	ctx.HTML(http.StatusOK, tplPackagesList)

routers/web/repo/projects.go

@@ -118,7 +118,7 @@ func Projects(ctx *context.Context) {
 	}
 
 	pager := context.NewPagination(total, setting.UI.IssuePagingNum, page, numPages)
-	pager.AddParam(ctx, "state", "State")
+	pager.AddParamIfExist("state", ctx.Data["State"])
 	ctx.Data["Page"] = pager
 
 	ctx.Data["CanWriteProjects"] = ctx.Repo.Permission.CanWrite(unit.TypeProjects)

routers/web/repo/search.go

@@ -59,7 +59,7 @@ func Search(ctx *context.Context) {
 
 	pager := context.NewPagination(total, setting.UI.RepoSearchPagingNum, page, 5)
 	pager.SetDefaultParams(ctx)
-	pager.AddParam(ctx, "l", "Language")
+	pager.AddParamIfExist("l", ctx.Data["Language"])
 	ctx.Data["Page"] = pager
 
 	ctx.HTML(http.StatusOK, tplSearch)