Clean some functions about project issue (#27705)

1. remove unused function `MoveIssueAcrossProjectBoards`
2. extract the project board condition into a function
3. use db.NoCondition instead of -1. (BTW, the usage of db.NoCondition
is too confusing. Is there any way to avoid that?)
4. remove the unnecessary comment since the ctx refactor is completed.
5. Change `b.ID != 0` to `b.ID > 0`. It's more intuitive but I think
they're the same since board ID can't be negative.

2 files changed, 14 insertions, 36 deletions

diff --git a/models/issues/issue_project.go b/models/issues/issue_project.go
index 7906c3eace..cc7ffb356a 100644
--- a/models/issues/issue_project.go
+++ b/models/issues/issue_project.go
@@ -51,7 +51,7 @@ func (issue *Issue) ProjectBoardID(ctx context.Context) int64 {
 func LoadIssuesFromBoard(ctx context.Context, b *project_model.Board) (IssueList, error) {
 	issueList := make(IssueList, 0, 10)
 
-	if b.ID != 0 {
+	if b.ID > 0 {
 		issues, err := Issues(ctx, &IssuesOptions{
 			ProjectBoardID: b.ID,
 			ProjectID:      b.ProjectID,
@@ -65,7 +65,7 @@ func LoadIssuesFromBoard(ctx context.Context, b *project_model.Board) (IssueList
 
 	if b.Default {
 		issues, err := Issues(ctx, &IssuesOptions{
-			ProjectBoardID: -1, // Issues without ProjectBoardID
+			ProjectBoardID: db.NoConditionID,
 			ProjectID:      b.ProjectID,
 			SortType:       "project-column-sorting",
 		})
@@ -150,30 +150,3 @@ func addUpdateIssueProject(ctx context.Context, issue *Issue, doer *user_model.U
 		ProjectID: newProjectID,
 	})
 }
-
-// MoveIssueAcrossProjectBoards move a card from one board to another
-func MoveIssueAcrossProjectBoards(ctx context.Context, issue *Issue, board *project_model.Board) error {
-	ctx, committer, err := db.TxContext(ctx)
-	if err != nil {
-		return err
-	}
-	defer committer.Close()
-	sess := db.GetEngine(ctx)
-
-	var pis project_model.ProjectIssue
-	has, err := sess.Where("issue_id=?", issue.ID).Get(&pis)
-	if err != nil {
-		return err
-	}
-
-	if !has {
-		return fmt.Errorf("issue has to be added to a project first")
-	}
-
-	pis.ProjectBoardID = board.ID
-	if _, err := sess.ID(pis.ID).Cols("project_board_id").Update(&pis); err != nil {
-		return err
-	}
-
-	return committer.Commit()
-}
diff --git a/models/issues/issue_search.go b/models/issues/issue_search.go
index 3e878ff1e7..9b6bf117b1 100644
--- a/models/issues/issue_search.go
+++ b/models/issues/issue_search.go
@@ -180,6 +180,17 @@ func applyProjectCondition(sess *xorm.Session, opts *IssuesOptions) *xorm.Sessio
 	return sess
 }
 
+func applyProjectBoardCondition(sess *xorm.Session, opts *IssuesOptions) *xorm.Session {
+	// opts.ProjectBoardID == 0 means all project boards,
+	// do not need to apply any condition
+	if opts.ProjectBoardID > 0 {
+		sess.In("issue.id", builder.Select("issue_id").From("project_issue").Where(builder.Eq{"project_board_id": opts.ProjectBoardID}))
+	} else if opts.ProjectBoardID == db.NoConditionID {
+		sess.In("issue.id", builder.Select("issue_id").From("project_issue").Where(builder.Neq{"project_board_id": 0}))
+	}
+	return sess
+}
+
 func applyRepoConditions(sess *xorm.Session, opts *IssuesOptions) *xorm.Session {
 	if len(opts.RepoIDs) == 1 {
 		opts.RepoCond = builder.Eq{"issue.repo_id": opts.RepoIDs[0]}
@@ -240,13 +251,7 @@ func applyConditions(sess *xorm.Session, opts *IssuesOptions) *xorm.Session {
 
 	applyProjectCondition(sess, opts)
 
-	if opts.ProjectBoardID != 0 {
-		if opts.ProjectBoardID > 0 {
-			sess.In("issue.id", builder.Select("issue_id").From("project_issue").Where(builder.Eq{"project_board_id": opts.ProjectBoardID}))
-		} else {
-			sess.In("issue.id", builder.Select("issue_id").From("project_issue").Where(builder.Eq{"project_board_id": 0}))
-		}
-	}
+	applyProjectBoardCondition(sess, opts)
 
 	switch opts.IsPull {
 	case util.OptionalBoolTrue: