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

2 files changed, 27 insertions, 3 deletions

diff --git a/routers/api/v1/api.go b/routers/api/v1/api.go
index 588a763616..8a300f9958 100644
--- a/routers/api/v1/api.go
+++ b/routers/api/v1/api.go
@@ -477,7 +477,7 @@ func RegisterRoutes(m *macaron.Macaron) {
 						m.Combo("").Get(repo.GetPullRequest).
 							Patch(reqToken(), reqRepoWriter(), bind(api.EditPullRequestOption{}), repo.EditPullRequest)
 						m.Combo("/merge").Get(repo.IsPullRequestMerged).
-							Post(reqToken(), reqRepoWriter(), repo.MergePullRequest)
+							Post(reqToken(), reqRepoWriter(), bind(auth.MergePullRequestForm{}), repo.MergePullRequest)
 					})
 
 				}, mustAllowPulls, context.ReferencesGitRepo())
diff --git a/routers/api/v1/repo/pull.go b/routers/api/v1/repo/pull.go
index 50b864e323..7e011219be 100644
--- a/routers/api/v1/repo/pull.go
+++ b/routers/api/v1/repo/pull.go
@@ -10,6 +10,7 @@ import (
 
 	"code.gitea.io/git"
 	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/auth"
 	"code.gitea.io/gitea/modules/context"
 	"code.gitea.io/gitea/modules/log"
 
@@ -434,7 +435,7 @@ func IsPullRequestMerged(ctx *context.APIContext) {
 }
 
 // MergePullRequest merges a PR given an index
-func MergePullRequest(ctx *context.APIContext) {
+func MergePullRequest(ctx *context.APIContext, form auth.MergePullRequestForm) {
 	// swagger:operation POST /repos/{owner}/{repo}/pulls/{index}/merge repository repoMergePullRequest
 	// ---
 	// summary: Merge a pull request
@@ -497,7 +498,30 @@ func MergePullRequest(ctx *context.APIContext) {
 		return
 	}
 
-	if err := pr.Merge(ctx.User, ctx.Repo.GitRepo); err != nil {
+	if len(form.Do) == 0 {
+		form.Do = string(models.MergeStyleMerge)
+	}
+
+	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
+	}
+
+	if err := pr.Merge(ctx.User, ctx.Repo.GitRepo, models.MergeStyle(form.Do), message); err != nil {
+		if models.IsErrInvalidMergeStyle(err) {
+			ctx.Status(405)
+			return
+		}
 		ctx.Error(500, "Merge", err)
 		return
 	}