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

6 files changed, 83 insertions, 7 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
 	}
diff --git a/routers/repo/issue.go b/routers/repo/issue.go
index 530586a143..e4aecf152e 100644
--- a/routers/repo/issue.go
+++ b/routers/repo/issue.go
@@ -727,6 +727,26 @@ func ViewIssue(ctx *context.Context) {
 			}
 		}
 
+		prUnit, err := repo.GetUnit(models.UnitTypePullRequests)
+		if err != nil {
+			ctx.Handle(500, "GetUnit", err)
+			return
+		}
+		prConfig := prUnit.PullRequestsConfig()
+
+		// Check correct values and select default
+		if ms, ok := ctx.Data["MergeStyle"].(models.MergeStyle); !ok ||
+			!prConfig.IsMergeStyleAllowed(ms) {
+			if prConfig.AllowMerge {
+				ctx.Data["MergeStyle"] = models.MergeStyleMerge
+			} else if prConfig.AllowRebase {
+				ctx.Data["MergeStyle"] = models.MergeStyleRebase
+			} else if prConfig.AllowSquash {
+				ctx.Data["MergeStyle"] = models.MergeStyleSquash
+			} else {
+				ctx.Data["MergeStyle"] = ""
+			}
+		}
 		ctx.Data["IsPullBranchDeletable"] = canDelete && pull.HeadRepo != nil && git.IsBranchExist(pull.HeadRepo.RepoPath(), pull.HeadBranch)
 	}
 
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
 	}
diff --git a/routers/repo/setting.go b/routers/repo/setting.go
index 8cb551707c..342451b8ad 100644
--- a/routers/repo/setting.go
+++ b/routers/repo/setting.go
@@ -211,7 +211,12 @@ func SettingsPost(ctx *context.Context, form auth.RepoSettingForm) {
 			units = append(units, models.RepoUnit{
 				RepoID: repo.ID,
 				Type:   models.UnitTypePullRequests,
-				Config: new(models.UnitConfig),
+				Config: &models.PullRequestsConfig{
+					IgnoreWhitespaceConflicts: form.PullsIgnoreWhitespace,
+					AllowMerge:                form.PullsAllowMerge,
+					AllowRebase:               form.PullsAllowRebase,
+					AllowSquash:               form.PullsAllowSquash,
+				},
 			})
 		}
 
diff --git a/routers/routes/routes.go b/routers/routes/routes.go
index 4293cca6c9..3e00f55ebf 100644
--- a/routers/routes/routes.go
+++ b/routers/routes/routes.go
@@ -627,7 +627,7 @@ func RegisterRoutes(m *macaron.Macaron) {
 			m.Get(".diff", repo.DownloadPullDiff)
 			m.Get("/commits", context.RepoRef(), repo.ViewPullCommits)
 			m.Get("/files", context.RepoRef(), repo.SetEditorconfigIfExists, repo.SetDiffViewStyle, repo.ViewPullFiles)
-			m.Post("/merge", reqRepoWriter, repo.MergePullRequest)
+			m.Post("/merge", reqRepoWriter, bindIgnErr(auth.MergePullRequestForm{}), repo.MergePullRequest)
 			m.Post("/cleanup", context.RepoRef(), repo.CleanUpPullRequest)
 		}, repo.MustAllowPulls)