DBContext is just a Context (#17100)

* DBContext is just a Context

This PR removes some of the specialness from the DBContext and makes it context
This allows us to simplify the GetEngine code to wrap around any context in future
and means that we can change our loadRepo(e Engine) functions to simply take contexts.

Signed-off-by: Andrew Thornton <art27@cantab.net>

* fix unit tests

Signed-off-by: Andrew Thornton <art27@cantab.net>

* another place that needs to set the initial context

Signed-off-by: Andrew Thornton <art27@cantab.net>

* avoid race

Signed-off-by: Andrew Thornton <art27@cantab.net>

* change attachment error

Signed-off-by: Andrew Thornton <art27@cantab.net>

models/protected_tag.go

@@ -35,19 +35,19 @@ func init() {
 
 // InsertProtectedTag inserts a protected tag to database
 func InsertProtectedTag(pt *ProtectedTag) error {
-	_, err := db.DefaultContext().Engine().Insert(pt)
+	_, err := db.GetEngine(db.DefaultContext).Insert(pt)
 	return err
 }
 
 // UpdateProtectedTag updates the protected tag
 func UpdateProtectedTag(pt *ProtectedTag) error {
-	_, err := db.DefaultContext().Engine().ID(pt.ID).AllCols().Update(pt)
+	_, err := db.GetEngine(db.DefaultContext).ID(pt.ID).AllCols().Update(pt)
 	return err
 }
 
 // DeleteProtectedTag deletes a protected tag by ID
 func DeleteProtectedTag(pt *ProtectedTag) error {
-	_, err := db.DefaultContext().Engine().ID(pt.ID).Delete(&ProtectedTag{})
+	_, err := db.GetEngine(db.DefaultContext).ID(pt.ID).Delete(&ProtectedTag{})
 	return err
 }
 
@@ -86,13 +86,13 @@ func (pt *ProtectedTag) IsUserAllowed(userID int64) (bool, error) {
 // GetProtectedTags gets all protected tags of the repository
 func (repo *Repository) GetProtectedTags() ([]*ProtectedTag, error) {
 	tags := make([]*ProtectedTag, 0)
-	return tags, db.DefaultContext().Engine().Find(&tags, &ProtectedTag{RepoID: repo.ID})
+	return tags, db.GetEngine(db.DefaultContext).Find(&tags, &ProtectedTag{RepoID: repo.ID})
 }
 
 // GetProtectedTagByID gets the protected tag with the specific id
 func GetProtectedTagByID(id int64) (*ProtectedTag, error) {
 	tag := new(ProtectedTag)
-	has, err := db.DefaultContext().Engine().ID(id).Get(tag)
+	has, err := db.GetEngine(db.DefaultContext).ID(id).Get(tag)
 	if err != nil {
 		return nil, err
 	}