Add error for fork already existing (#7185)

models/error.go

@@ -674,6 +674,23 @@ func (err ErrRepoAlreadyExist) Error() string {
 	return fmt.Sprintf("repository already exists [uname: %s, name: %s]", err.Uname, err.Name)
 }
 
+// ErrForkAlreadyExist represents a "ForkAlreadyExist" kind of error.
+type ErrForkAlreadyExist struct {
+	Uname    string
+	RepoName string
+	ForkName string
+}
+
+// IsErrForkAlreadyExist checks if an error is an ErrForkAlreadyExist.
+func IsErrForkAlreadyExist(err error) bool {
+	_, ok := err.(ErrForkAlreadyExist)
+	return ok
+}
+
+func (err ErrForkAlreadyExist) Error() string {
+	return fmt.Sprintf("repository is already forked by user [uname: %s, repo path: %s, fork path: %s]", err.Uname, err.RepoName, err.ForkName)
+}
+
 // ErrRepoRedirectNotExist represents a "RepoRedirectNotExist" kind of error.
 type ErrRepoRedirectNotExist struct {
 	OwnerID  int64

models/repo.go

@@ -2395,9 +2395,10 @@ func ForkRepository(doer, u *User, oldRepo *Repository, name, desc string) (_ *R
 		return nil, err
 	}
 	if forkedRepo != nil {
-		return nil, ErrRepoAlreadyExist{
-			Uname: u.Name,
-			Name:  forkedRepo.Name,
+		return nil, ErrForkAlreadyExist{
+			Uname:    u.Name,
+			RepoName: oldRepo.FullName(),
+			ForkName: forkedRepo.FullName(),
 		}
 	}
 

models/repo_test.go

@@ -131,7 +131,7 @@ func TestForkRepository(t *testing.T) {
 	fork, err := ForkRepository(user, user, repo, "test", "test")
 	assert.Nil(t, fork)
 	assert.Error(t, err)
-	assert.True(t, IsErrRepoAlreadyExist(err))
+	assert.True(t, IsErrForkAlreadyExist(err))
 }
 
 func TestRepoAPIURL(t *testing.T) {