Add Pull Request merge options - Ignore white-space for conflict checking, Rebase, Squash merge (#3188)

* Pull request options migration and UI in settings

* Add ignore whitespace functionality

* Fix settings if pull requests are disabled

* Fix migration transaction

* Merge with Rebase functionality

* UI changes and related functionality for pull request merging button

* Implement squash functionality

* Fix rebase merging

* Fix pull request merge tests

* Add squash and rebase tests

* Fix API method to reuse default message functions

* Some refactoring and small fixes

* Remove more hardcoded values from tests

* Remove unneeded check from API method

* Fix variable name and comment typo

* Fix reset commit count after PR merge

1 files changed, 17 insertions, 0 deletions

diff --git a/models/error.go b/models/error.go
index fceee21fdf..765b8fa6ca 100644
--- a/models/error.go
+++ b/models/error.go
@@ -878,6 +878,23 @@ func (err ErrPullRequestAlreadyExists) Error() string {
 		err.ID, err.IssueID, err.HeadRepoID, err.BaseRepoID, err.HeadBranch, err.BaseBranch)
 }
 
+// ErrInvalidMergeStyle represents an error if merging with disabled merge strategy
+type ErrInvalidMergeStyle struct {
+	ID    int64
+	Style MergeStyle
+}
+
+// IsErrInvalidMergeStyle checks if an error is a ErrInvalidMergeStyle.
+func IsErrInvalidMergeStyle(err error) bool {
+	_, ok := err.(ErrInvalidMergeStyle)
+	return ok
+}
+
+func (err ErrInvalidMergeStyle) Error() string {
+	return fmt.Sprintf("merge strategy is not allowed or is invalid [repo_id: %d, strategy: %s]",
+		err.ID, err.Style)
+}
+
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