Fix #2001 and fix issue comments hidden (#2016)

* revert #2001 and fix issue comments hidden

* fix #2001

* fix import

* improve comment type

* reduce unnecessary join

* fix comment on FindCommentsOptions

models/issue.go

 	}
 
 	if issue.Comments == nil {
-		issue.Comments, err = getCommentsByIssueID(e, issue.ID)
+		issue.Comments, err = findComments(e, FindCommentsOptions{
+			IssueID: issue.ID,
+			Type:    CommentTypeUnknown,
+		})
 		if err != nil {
 			return fmt.Errorf("getCommentsByIssueID [%d]: %v", issue.ID, err)
 		}

models/issue_comment.go

 	"time"
 
 	"github.com/Unknwon/com"
+	"github.com/go-xorm/builder"
 	"github.com/go-xorm/xorm"
 
 	api "code.gitea.io/sdk/gitea"
 // CommentType defines whether a comment is just a simple comment, an action (like close) or a reference.
 type CommentType int
 
+// define unknown comment type
+const (
+	CommentTypeUnknown CommentType = -1
+)
+
 // Enumerate all the comment types
 const (
 	// Plain comment, can be associated with a commit (CommitID > 0) and a line (LineNum > 0)
 	return c, nil
 }
 
-func getCommentsByIssueIDSince(e Engine, issueID, since int64) ([]*Comment, error) {
-	comments := make([]*Comment, 0, 10)
-	sess := e.
-		Where("issue_id = ?", issueID).
-		Where("type = ?", CommentTypeComment).
-		Asc("created_unix")
-	if since > 0 {
-		sess.And("updated_unix >= ?", since)
+// FindCommentsOptions describes the conditions to Find comments
+type FindCommentsOptions struct {
+	RepoID  int64
+	IssueID int64
+	Since   int64
+	Type    CommentType
+}
+
+func (opts *FindCommentsOptions) toConds() builder.Cond {
+	var cond = builder.NewCond()
+	if opts.RepoID > 0 {
+		cond = cond.And(builder.Eq{"issue.repo_id": opts.RepoID})
 	}
-	return comments, sess.Find(&comments)
+	if opts.IssueID > 0 {
+		cond = cond.And(builder.Eq{"comment.issue_id": opts.IssueID})
+	}
+	if opts.Since > 0 {
+		cond = cond.And(builder.Gte{"comment.updated_unix": opts.Since})
+	}
+	if opts.Type != CommentTypeUnknown {
+		cond = cond.And(builder.Eq{"comment.type": opts.Type})
+	}
+	return cond
 }
 
-func getCommentsByRepoIDSince(e Engine, repoID, since int64) ([]*Comment, error) {
+func findComments(e Engine, opts FindCommentsOptions) ([]*Comment, error) {
 	comments := make([]*Comment, 0, 10)
-	sess := e.Where("issue.repo_id = ?", repoID).
-		Where("comment.type = ?", CommentTypeComment).
-		Join("INNER", "issue", "issue.id = comment.issue_id").
-		Asc("comment.created_unix")
-	if since > 0 {
-		sess.And("comment.updated_unix >= ?", since)
+	sess := e.Where(opts.toConds())
+	if opts.RepoID > 0 {
+		sess.Join("INNER", "issue", "issue.id = comment.issue_id")
 	}
-	return comments, sess.Find(&comments)
+	return comments, sess.
+		Asc("comment.created_unix").
+		Find(&comments)
 }
 
-func getCommentsByIssueID(e Engine, issueID int64) ([]*Comment, error) {
-	return getCommentsByIssueIDSince(e, issueID, -1)
+// FindComments returns all comments according options
+func FindComments(opts FindCommentsOptions) ([]*Comment, error) {
+	return findComments(x, opts)
 }
 
 // GetCommentsByIssueID returns all comments of an issue.
 func GetCommentsByIssueID(issueID int64) ([]*Comment, error) {
-	return getCommentsByIssueID(x, issueID)
+	return findComments(x, FindCommentsOptions{
+		IssueID: issueID,
+		Type:    CommentTypeUnknown,
+	})
 }
 
 // GetCommentsByIssueIDSince returns a list of comments of an issue since a given time point.
 func GetCommentsByIssueIDSince(issueID, since int64) ([]*Comment, error) {
-	return getCommentsByIssueIDSince(x, issueID, since)
+	return findComments(x, FindCommentsOptions{
+		IssueID: issueID,
+		Type:    CommentTypeUnknown,
+		Since:   since,
+	})
 }
 
 // GetCommentsByRepoIDSince returns a list of comments for all issues in a repo since a given time point.
 func GetCommentsByRepoIDSince(repoID, since int64) ([]*Comment, error) {
-	return getCommentsByRepoIDSince(x, repoID, since)
+	return findComments(x, FindCommentsOptions{
+		RepoID: repoID,
+		Type:   CommentTypeUnknown,
+		Since:  since,
+	})
 }
 
 // UpdateComment updates information of comment.

routers/api/v1/repo/issue_comment.go

 		return
 	}
 
-	comments, err := models.GetCommentsByIssueIDSince(issue.ID, since.Unix())
+	comments, err := models.FindComments(models.FindCommentsOptions{
+		IssueID: issue.ID,
+		Since:   since.Unix(),
+		Type:    models.CommentTypeComment,
+	})
 	if err != nil {
 		ctx.Error(500, "GetCommentsByIssueIDSince", err)
 		return
 		since, _ = time.Parse(time.RFC3339, ctx.Query("since"))
 	}
 
-	comments, err := models.GetCommentsByRepoIDSince(ctx.Repo.Repository.ID, since.Unix())
+	comments, err := models.FindComments(models.FindCommentsOptions{
+		RepoID: ctx.Repo.Repository.ID,
+		Since:  since.Unix(),
+		Type:   models.CommentTypeComment,
+	})
 	if err != nil {
 		ctx.Error(500, "GetCommentsByRepoIDSince", err)
 		return