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, 29 insertions, 2 deletions

diff --git a/routers/repo/pull.go b/routers/repo/pull.go
index 6162df9651..9de8268957 100644
--- a/routers/repo/pull.go
+++ b/routers/repo/pull.go
@@ -495,7 +495,7 @@ func ViewPullFiles(ctx *context.Context) {
 }
 
 // MergePullRequest response for merging pull request
-func MergePullRequest(ctx *context.Context) {
+func MergePullRequest(ctx *context.Context, form auth.MergePullRequestForm) {
 	issue := checkPullInfo(ctx)
 	if ctx.Written() {
 		return
@@ -514,15 +514,42 @@ func MergePullRequest(ctx *context.Context) {
 		}
 		return
 	}
+	pr.Issue = issue
 
 	if !pr.CanAutoMerge() || pr.HasMerged {
 		ctx.Handle(404, "MergePullRequest", nil)
 		return
 	}
 
+	if ctx.HasError() {
+		ctx.Flash.Error(ctx.Data["ErrorMsg"].(string))
+		ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
+		return
+	}
+
+	message := strings.TrimSpace(form.MergeTitleField)
+	if len(message) == 0 {
+		if models.MergeStyle(form.Do) == models.MergeStyleMerge {
+			message = pr.GetDefaultMergeMessage()
+		}
+		if models.MergeStyle(form.Do) == models.MergeStyleSquash {
+			message = pr.GetDefaultSquashMessage()
+		}
+	}
+
+	form.MergeMessageField = strings.TrimSpace(form.MergeMessageField)
+	if len(form.MergeMessageField) > 0 {
+		message += "\n\n" + form.MergeMessageField
+	}
+
 	pr.Issue = issue
 	pr.Issue.Repo = ctx.Repo.Repository
-	if err = pr.Merge(ctx.User, ctx.Repo.GitRepo); err != nil {
+	if err = pr.Merge(ctx.User, ctx.Repo.GitRepo, models.MergeStyle(form.Do), message); err != nil {
+		if models.IsErrInvalidMergeStyle(err) {
+			ctx.Flash.Error(ctx.Tr("repo.pulls.invalid_merge_option"))
+			ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
+			return
+		}
 		ctx.Handle(500, "Merge", err)
 		return
 	}