feat: allow changing default branch update style

This commit allows chaning default branch update style through global
and repository settings. The setting affects "Update branch" button
in PR view (button shows when some commits are ahead of master branch).
When default update style is set to "rebase", dropdown button updates branch
by rebase by default. When update style is set to other value, dropdown button
updates branch by merge. Any of these actions may be selected using dropdown
in any case.

Signed-off-by: George Bartolomey <george@bh4.ru>

models/repo/git.go

@@ -29,6 +29,15 @@ const (
 	MergeStyleRebaseUpdate MergeStyle = "rebase-update-only"
 )
 
+type UpdateStyle string
+
+const (
+	// UpdateStyleMerge create merge commit to update
+	UpdateStyleMerge UpdateStyle = "merge"
+	// UpdateStyleRebase rebase to update
+	UpdateStyleRebase UpdateStyle = "rebase"
+)
+
 // UpdateDefaultBranch updates the default branch
 func UpdateDefaultBranch(ctx context.Context, repo *Repository) error {
 	_, err := db.GetEngine(ctx).ID(repo.ID).Cols("default_branch").Update(repo)

models/repo/repo_unit.go

@@ -159,6 +159,7 @@ type PullRequestsConfig struct {
 	AllowRebaseUpdate             bool
 	DefaultDeleteBranchAfterMerge bool
 	DefaultMergeStyle             MergeStyle
+	DefaultUpdateStyle            UpdateStyle
 	DefaultAllowMaintainerEdit    bool
 }
 
@@ -197,6 +198,25 @@ func (cfg *PullRequestsConfig) GetDefaultMergeStyle() MergeStyle {
 	return MergeStyleMerge
 }
 
+// IsUpdateStyleAllowed returns if update style is allowed
+func (cfg *PullRequestsConfig) IsUpdateStyleAllowed(updateStyle UpdateStyle) bool {
+	return updateStyle == UpdateStyleMerge ||
+		updateStyle == UpdateStyleRebase && cfg.AllowRebaseUpdate
+}
+
+// GetDefaultUpdateStyle returns the default update style for this pull request
+func (cfg *PullRequestsConfig) GetDefaultUpdateStyle() UpdateStyle {
+	if len(cfg.DefaultUpdateStyle) != 0 {
+		return cfg.DefaultUpdateStyle
+	}
+
+	if setting.Repository.PullRequest.DefaultUpdateStyle != "" {
+		return UpdateStyle(setting.Repository.PullRequest.DefaultUpdateStyle)
+	}
+
+	return UpdateStyleMerge
+}
+
 type ActionsConfig struct {
 	DisabledWorkflows []string
 }

models/repo/repo_unit_test.go

@@ -7,6 +7,8 @@ import (
 	"testing"
 
 	"code.gitea.io/gitea/models/perm"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -37,3 +39,50 @@ func TestRepoUnitAccessMode(t *testing.T) {
 	assert.Equal(t, perm.AccessModeWrite, UnitAccessModeWrite.ToAccessMode(perm.AccessModeAdmin))
 	assert.Equal(t, perm.AccessModeRead, UnitAccessModeUnset.ToAccessMode(perm.AccessModeRead))
 }
+
+func TestRepoPRIsUpdateStyleAllowed(t *testing.T) {
+	var cfg PullRequestsConfig
+	cfg = PullRequestsConfig{
+		AllowRebaseUpdate: true,
+	}
+	assert.True(t, cfg.IsUpdateStyleAllowed(UpdateStyleMerge))
+	assert.True(t, cfg.IsUpdateStyleAllowed(UpdateStyleRebase))
+
+	cfg = PullRequestsConfig{
+		AllowRebaseUpdate: false,
+	}
+	assert.True(t, cfg.IsUpdateStyleAllowed(UpdateStyleMerge))
+	assert.False(t, cfg.IsUpdateStyleAllowed(UpdateStyleRebase))
+}
+
+func TestRepoPRGetDefaultUpdateStyle(t *testing.T) {
+	defer test.MockVariableValue(&setting.Repository.PullRequest.DefaultUpdateStyle, "merge")()
+
+	var cfg PullRequestsConfig
+	cfg = PullRequestsConfig{
+		DefaultUpdateStyle: "",
+	}
+	assert.Equal(t, UpdateStyleMerge, cfg.GetDefaultUpdateStyle())
+	cfg = PullRequestsConfig{
+		DefaultUpdateStyle: "rebase",
+	}
+	assert.Equal(t, UpdateStyleRebase, cfg.GetDefaultUpdateStyle())
+	cfg = PullRequestsConfig{
+		DefaultUpdateStyle: "merge",
+	}
+	assert.Equal(t, UpdateStyleMerge, cfg.GetDefaultUpdateStyle())
+
+	setting.Repository.PullRequest.DefaultUpdateStyle = "rebase"
+	cfg = PullRequestsConfig{
+		DefaultUpdateStyle: "",
+	}
+	assert.Equal(t, UpdateStyleRebase, cfg.GetDefaultUpdateStyle())
+	cfg = PullRequestsConfig{
+		DefaultUpdateStyle: "rebase",
+	}
+	assert.Equal(t, UpdateStyleRebase, cfg.GetDefaultUpdateStyle())
+	cfg = PullRequestsConfig{
+		DefaultUpdateStyle: "merge",
+	}
+	assert.Equal(t, UpdateStyleMerge, cfg.GetDefaultUpdateStyle())
+}