Edit file workflow for creating a fork and proposing changes (#34240)

When viewing a file that the user can't edit because they can't write to
the branch, the new, upload, patch, edit and delete functionality is no
longer disabled.

If no user fork of the repository exists, there is now a page to create one.
It will automatically create a fork with a single branch matching the one
being viewed, and a unique repository name will be automatically picked.

When a fork exists, but it's archived, a mirror or the user can't write
code to it, there will instead be a message explaining the situation.

If the usable fork exists, a message will appear at the top of the edit page
explaining that the changes will be applied to a branch in the fork. The
base repository branch will be pushed to a new branch to the fork, and
then the edits will be applied on top.

The suggestion to fork happens when accessing /_edit/, so that for
example online documentation can have an "edit this page" link to
the base repository that does the right thing.

Also includes changes to properly report errors when trying to commit
to a new branch that is protected, and when trying to commit to an
existing branch when choosing the new branch option.

Resolves #9017, #20882

---------

Co-authored-by: Brecht Van Lommel <brecht@blender.org>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/editor.go

@@ -16,6 +16,7 @@ import (
 	"code.gitea.io/gitea/modules/charset"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/httplib"
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/markup"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/templates"
@@ -39,7 +40,7 @@ const (
 	editorCommitChoiceNewBranch string = "commit-to-new-branch"
 )
 
-func prepareEditorCommitFormOptions(ctx *context.Context, editorAction string) {
+func prepareEditorCommitFormOptions(ctx *context.Context, editorAction string) *context.CommitFormOptions {
 	cleanedTreePath := files_service.CleanGitTreePath(ctx.Repo.TreePath)
 	if cleanedTreePath != ctx.Repo.TreePath {
 		redirectTo := fmt.Sprintf("%s/%s/%s/%s", ctx.Repo.RepoLink, editorAction, util.PathEscapeSegments(ctx.Repo.BranchName), util.PathEscapeSegments(cleanedTreePath))
@@ -47,18 +48,28 @@ func prepareEditorCommitFormOptions(ctx *context.Context, editorAction string) {
 			redirectTo += "?" + ctx.Req.URL.RawQuery
 		}
 		ctx.Redirect(redirectTo)
-		return
+		return nil
 	}
 
-	commitFormBehaviors, err := ctx.Repo.PrepareCommitFormBehaviors(ctx, ctx.Doer)
+	commitFormOptions, err := context.PrepareCommitFormOptions(ctx, ctx.Doer, ctx.Repo.Repository, ctx.Repo.Permission, ctx.Repo.RefFullName)
 	if err != nil {
-		ctx.ServerError("PrepareCommitFormBehaviors", err)
-		return
+		ctx.ServerError("PrepareCommitFormOptions", err)
+		return nil
+	}
+
+	if commitFormOptions.NeedFork {
+		ForkToEdit(ctx)
+		return nil
+	}
+
+	if commitFormOptions.WillSubmitToFork && !commitFormOptions.TargetRepo.CanEnableEditor() {
+		ctx.Data["NotFoundPrompt"] = ctx.Locale.Tr("repo.editor.fork_not_editable")
+		ctx.NotFound(nil)
 	}
 
 	ctx.Data["BranchLink"] = ctx.Repo.RepoLink + "/src/" + ctx.Repo.RefTypeNameSubURL()
 	ctx.Data["TreePath"] = ctx.Repo.TreePath
-	ctx.Data["CommitFormBehaviors"] = commitFormBehaviors
+	ctx.Data["CommitFormOptions"] = commitFormOptions
 
 	// for online editor
 	ctx.Data["PreviewableExtensions"] = strings.Join(markup.PreviewableExtensions(), ",")
@@ -69,25 +80,27 @@ func prepareEditorCommitFormOptions(ctx *context.Context, editorAction string) {
 	// form fields
 	ctx.Data["commit_summary"] = ""
 	ctx.Data["commit_message"] = ""
-	ctx.Data["commit_choice"] = util.Iif(commitFormBehaviors.CanCommitToBranch, editorCommitChoiceDirect, editorCommitChoiceNewBranch)
-	ctx.Data["new_branch_name"] = getUniquePatchBranchName(ctx, ctx.Doer.LowerName, ctx.Repo.Repository)
+	ctx.Data["commit_choice"] = util.Iif(commitFormOptions.CanCommitToBranch, editorCommitChoiceDirect, editorCommitChoiceNewBranch)
+	ctx.Data["new_branch_name"] = getUniquePatchBranchName(ctx, ctx.Doer.LowerName, commitFormOptions.TargetRepo)
 	ctx.Data["last_commit"] = ctx.Repo.CommitID
+	return commitFormOptions
 }
 
 func prepareTreePathFieldsAndPaths(ctx *context.Context, treePath string) {
 	// show the tree path fields in the "breadcrumb" and help users to edit the target tree path
-	ctx.Data["TreeNames"], ctx.Data["TreePaths"] = getParentTreeFields(treePath)
+	ctx.Data["TreeNames"], ctx.Data["TreePaths"] = getParentTreeFields(strings.TrimPrefix(treePath, "/"))
 }
 
-type parsedEditorCommitForm[T any] struct {
-	form                T
-	commonForm          *forms.CommitCommonForm
-	CommitFormBehaviors *context.CommitFormBehaviors
-	TargetBranchName    string
-	GitCommitter        *files_service.IdentityOptions
+type preparedEditorCommitForm[T any] struct {
+	form              T
+	commonForm        *forms.CommitCommonForm
+	CommitFormOptions *context.CommitFormOptions
+	OldBranchName     string
+	NewBranchName     string
+	GitCommitter      *files_service.IdentityOptions
 }
 
-func (f *parsedEditorCommitForm[T]) GetCommitMessage(defaultCommitMessage string) string {
+func (f *preparedEditorCommitForm[T]) GetCommitMessage(defaultCommitMessage string) string {
 	commitMessage := util.IfZero(strings.TrimSpace(f.commonForm.CommitSummary), defaultCommitMessage)
 	if body := strings.TrimSpace(f.commonForm.CommitMessage); body != "" {
 		commitMessage += "\n\n" + body
@@ -95,7 +108,7 @@ func (f *parsedEditorCommitForm[T]) GetCommitMessage(defaultCommitMessage string
 	return commitMessage
 }
 
-func parseEditorCommitSubmittedForm[T forms.CommitCommonFormInterface](ctx *context.Context) *parsedEditorCommitForm[T] {
+func prepareEditorCommitSubmittedForm[T forms.CommitCommonFormInterface](ctx *context.Context) *preparedEditorCommitForm[T] {
 	form := web.GetForm(ctx).(T)
 	if ctx.HasError() {
 		ctx.JSONError(ctx.GetErrMsg())
@@ -105,15 +118,22 @@ func parseEditorCommitSubmittedForm[T forms.CommitCommonFormInterface](ctx *cont
 	commonForm := form.GetCommitCommonForm()
 	commonForm.TreePath = files_service.CleanGitTreePath(commonForm.TreePath)
 
-	commitFormBehaviors, err := ctx.Repo.PrepareCommitFormBehaviors(ctx, ctx.Doer)
+	commitFormOptions, err := context.PrepareCommitFormOptions(ctx, ctx.Doer, ctx.Repo.Repository, ctx.Repo.Permission, ctx.Repo.RefFullName)
 	if err != nil {
-		ctx.ServerError("PrepareCommitFormBehaviors", err)
+		ctx.ServerError("PrepareCommitFormOptions", err)
+		return nil
+	}
+	if commitFormOptions.NeedFork {
+		// It shouldn't happen, because we should have done the checks in the "GET" request. But just in case.
+		ctx.JSONError(ctx.Locale.TrString("error.not_found"))
 		return nil
 	}
 
 	// check commit behavior
-	targetBranchName := util.Iif(commonForm.CommitChoice == editorCommitChoiceNewBranch, commonForm.NewBranchName, ctx.Repo.BranchName)
-	if targetBranchName == ctx.Repo.BranchName && !commitFormBehaviors.CanCommitToBranch {
+	fromBaseBranch := ctx.FormString("from_base_branch")
+	commitToNewBranch := commonForm.CommitChoice == editorCommitChoiceNewBranch || fromBaseBranch != ""
+	targetBranchName := util.Iif(commitToNewBranch, commonForm.NewBranchName, ctx.Repo.BranchName)
+	if targetBranchName == ctx.Repo.BranchName && !commitFormOptions.CanCommitToBranch {
 		ctx.JSONError(ctx.Tr("repo.editor.cannot_commit_to_protected_branch", targetBranchName))
 		return nil
 	}
@@ -125,28 +145,63 @@ func parseEditorCommitSubmittedForm[T forms.CommitCommonFormInterface](ctx *cont
 		return nil
 	}
 
-	return &parsedEditorCommitForm[T]{
-		form:                form,
-		commonForm:          commonForm,
-		CommitFormBehaviors: commitFormBehaviors,
-		TargetBranchName:    targetBranchName,
-		GitCommitter:        gitCommitter,
+	if commitToNewBranch {
+		// if target branch exists, we should stop
+		targetBranchExists, err := git_model.IsBranchExist(ctx, commitFormOptions.TargetRepo.ID, targetBranchName)
+		if err != nil {
+			ctx.ServerError("IsBranchExist", err)
+			return nil
+		} else if targetBranchExists {
+			if fromBaseBranch != "" {
+				ctx.JSONError(ctx.Tr("repo.editor.fork_branch_exists", targetBranchName))
+			} else {
+				ctx.JSONError(ctx.Tr("repo.editor.branch_already_exists", targetBranchName))
+			}
+			return nil
+		}
+	}
+
+	oldBranchName := ctx.Repo.BranchName
+	if fromBaseBranch != "" {
+		err = editorPushBranchToForkedRepository(ctx, ctx.Doer, ctx.Repo.Repository.BaseRepo, fromBaseBranch, commitFormOptions.TargetRepo, targetBranchName)
+		if err != nil {
+			log.Error("Unable to editorPushBranchToForkedRepository: %v", err)
+			ctx.JSONError(ctx.Tr("repo.editor.fork_failed_to_push_branch", targetBranchName))
+			return nil
+		}
+		// we have pushed the base branch as the new branch, now we need to commit the changes directly to the new branch
+		oldBranchName = targetBranchName
+	}
+
+	return &preparedEditorCommitForm[T]{
+		form:              form,
+		commonForm:        commonForm,
+		CommitFormOptions: commitFormOptions,
+		OldBranchName:     oldBranchName,
+		NewBranchName:     targetBranchName,
+		GitCommitter:      gitCommitter,
 	}
 }
 
 // redirectForCommitChoice redirects after committing the edit to a branch
-func redirectForCommitChoice[T any](ctx *context.Context, parsed *parsedEditorCommitForm[T], treePath string) {
+func redirectForCommitChoice[T any](ctx *context.Context, parsed *preparedEditorCommitForm[T], treePath string) {
+	// when editing a file in a PR, it should return to the origin location
+	if returnURI := ctx.FormString("return_uri"); returnURI != "" && httplib.IsCurrentGiteaSiteURL(ctx, returnURI) {
+		ctx.JSONRedirect(returnURI)
+		return
+	}
+
 	if parsed.commonForm.CommitChoice == editorCommitChoiceNewBranch {
 		// Redirect to a pull request when possible
 		redirectToPullRequest := false
-		repo, baseBranch, headBranch := ctx.Repo.Repository, ctx.Repo.BranchName, parsed.TargetBranchName
-		if repo.UnitEnabled(ctx, unit.TypePullRequests) {
-			redirectToPullRequest = true
-		} else if parsed.CommitFormBehaviors.CanCreateBasePullRequest {
+		repo, baseBranch, headBranch := ctx.Repo.Repository, parsed.OldBranchName, parsed.NewBranchName
+		if ctx.Repo.Repository.IsFork && parsed.CommitFormOptions.CanCreateBasePullRequest {
 			redirectToPullRequest = true
 			baseBranch = repo.BaseRepo.DefaultBranch
 			headBranch = repo.Owner.Name + "/" + repo.Name + ":" + headBranch
 			repo = repo.BaseRepo
+		} else if repo.UnitEnabled(ctx, unit.TypePullRequests) {
+			redirectToPullRequest = true
 		}
 		if redirectToPullRequest {
 			ctx.JSONRedirect(repo.Link() + "/compare/" + util.PathEscapeSegments(baseBranch) + "..." + util.PathEscapeSegments(headBranch))
@@ -154,11 +209,9 @@ func redirectForCommitChoice[T any](ctx *context.Context, parsed *parsedEditorCo
 		}
 	}
 
-	returnURI := ctx.FormString("return_uri")
-	if returnURI == "" || !httplib.IsCurrentGiteaSiteURL(ctx, returnURI) {
-		returnURI = util.URLJoin(ctx.Repo.RepoLink, "src/branch", util.PathEscapeSegments(parsed.TargetBranchName), util.PathEscapeSegments(treePath))
-	}
-	ctx.JSONRedirect(returnURI)
+	// redirect to the newly updated file
+	redirectTo := util.URLJoin(ctx.Repo.RepoLink, "src/branch", util.PathEscapeSegments(parsed.NewBranchName), util.PathEscapeSegments(treePath))
+	ctx.JSONRedirect(redirectTo)
 }
 
 func editFileOpenExisting(ctx *context.Context) (prefetch []byte, dataRc io.ReadCloser, fInfo *fileInfo) {
@@ -268,7 +321,7 @@ func EditFile(ctx *context.Context) {
 func EditFilePost(ctx *context.Context) {
 	editorAction := ctx.PathParam("editor_action")
 	isNewFile := editorAction == "_new"
-	parsed := parseEditorCommitSubmittedForm[*forms.EditRepoFileForm](ctx)
+	parsed := prepareEditorCommitSubmittedForm[*forms.EditRepoFileForm](ctx)
 	if ctx.Written() {
 		return
 	}
@@ -292,8 +345,8 @@ func EditFilePost(ctx *context.Context) {
 
 	_, err := files_service.ChangeRepoFiles(ctx, ctx.Repo.Repository, ctx.Doer, &files_service.ChangeRepoFilesOptions{
 		LastCommitID: parsed.form.LastCommit,
-		OldBranch:    ctx.Repo.BranchName,
-		NewBranch:    parsed.TargetBranchName,
+		OldBranch:    parsed.OldBranchName,
+		NewBranch:    parsed.NewBranchName,
 		Message:      parsed.GetCommitMessage(defaultCommitMessage),
 		Files: []*files_service.ChangeRepoFile{
 			{
@@ -308,7 +361,7 @@ func EditFilePost(ctx *context.Context) {
 		Committer: parsed.GitCommitter,
 	})
 	if err != nil {
-		editorHandleFileOperationError(ctx, parsed.TargetBranchName, err)
+		editorHandleFileOperationError(ctx, parsed.NewBranchName, err)
 		return
 	}
 
@@ -327,7 +380,7 @@ func DeleteFile(ctx *context.Context) {
 
 // DeleteFilePost response for deleting file
 func DeleteFilePost(ctx *context.Context) {
-	parsed := parseEditorCommitSubmittedForm[*forms.DeleteRepoFileForm](ctx)
+	parsed := prepareEditorCommitSubmittedForm[*forms.DeleteRepoFileForm](ctx)
 	if ctx.Written() {
 		return
 	}
@@ -335,8 +388,8 @@ func DeleteFilePost(ctx *context.Context) {
 	treePath := ctx.Repo.TreePath
 	_, err := files_service.ChangeRepoFiles(ctx, ctx.Repo.Repository, ctx.Doer, &files_service.ChangeRepoFilesOptions{
 		LastCommitID: parsed.form.LastCommit,
-		OldBranch:    ctx.Repo.BranchName,
-		NewBranch:    parsed.TargetBranchName,
+		OldBranch:    parsed.OldBranchName,
+		NewBranch:    parsed.NewBranchName,
 		Files: []*files_service.ChangeRepoFile{
 			{
 				Operation: "delete",
@@ -349,29 +402,29 @@ func DeleteFilePost(ctx *context.Context) {
 		Committer: parsed.GitCommitter,
 	})
 	if err != nil {
-		editorHandleFileOperationError(ctx, parsed.TargetBranchName, err)
+		editorHandleFileOperationError(ctx, parsed.NewBranchName, err)
 		return
 	}
 
 	ctx.Flash.Success(ctx.Tr("repo.editor.file_delete_success", treePath))
-	redirectTreePath := getClosestParentWithFiles(ctx.Repo.GitRepo, parsed.TargetBranchName, treePath)
+	redirectTreePath := getClosestParentWithFiles(ctx.Repo.GitRepo, parsed.NewBranchName, treePath)
 	redirectForCommitChoice(ctx, parsed, redirectTreePath)
 }
 
 func UploadFile(ctx *context.Context) {
 	ctx.Data["PageIsUpload"] = true
-	upload.AddUploadContext(ctx, "repo")
 	prepareTreePathFieldsAndPaths(ctx, ctx.Repo.TreePath)
-
-	prepareEditorCommitFormOptions(ctx, "_upload")
+	opts := prepareEditorCommitFormOptions(ctx, "_upload")
 	if ctx.Written() {
 		return
 	}
+	upload.AddUploadContextForRepo(ctx, opts.TargetRepo)
+
 	ctx.HTML(http.StatusOK, tplUploadFile)
 }
 
 func UploadFilePost(ctx *context.Context) {
-	parsed := parseEditorCommitSubmittedForm[*forms.UploadRepoFileForm](ctx)
+	parsed := prepareEditorCommitSubmittedForm[*forms.UploadRepoFileForm](ctx)
 	if ctx.Written() {
 		return
 	}
@@ -379,8 +432,8 @@ func UploadFilePost(ctx *context.Context) {
 	defaultCommitMessage := ctx.Locale.TrString("repo.editor.upload_files_to_dir", util.IfZero(parsed.form.TreePath, "/"))
 	err := files_service.UploadRepoFiles(ctx, ctx.Repo.Repository, ctx.Doer, &files_service.UploadRepoFileOptions{
 		LastCommitID: parsed.form.LastCommit,
-		OldBranch:    ctx.Repo.BranchName,
-		NewBranch:    parsed.TargetBranchName,
+		OldBranch:    parsed.OldBranchName,
+		NewBranch:    parsed.NewBranchName,
 		TreePath:     parsed.form.TreePath,
 		Message:      parsed.GetCommitMessage(defaultCommitMessage),
 		Files:        parsed.form.Files,
@@ -389,7 +442,7 @@ func UploadFilePost(ctx *context.Context) {
 		Committer:    parsed.GitCommitter,
 	})
 	if err != nil {
-		editorHandleFileOperationError(ctx, parsed.TargetBranchName, err)
+		editorHandleFileOperationError(ctx, parsed.NewBranchName, err)
 		return
 	}
 	redirectForCommitChoice(ctx, parsed, parsed.form.TreePath)

routers/web/repo/editor_apply_patch.go

@@ -25,7 +25,7 @@ func NewDiffPatch(ctx *context.Context) {
 
 // NewDiffPatchPost response for sending patch page
 func NewDiffPatchPost(ctx *context.Context) {
-	parsed := parseEditorCommitSubmittedForm[*forms.EditRepoFileForm](ctx)
+	parsed := prepareEditorCommitSubmittedForm[*forms.EditRepoFileForm](ctx)
 	if ctx.Written() {
 		return
 	}
@@ -33,8 +33,8 @@ func NewDiffPatchPost(ctx *context.Context) {
 	defaultCommitMessage := ctx.Locale.TrString("repo.editor.patch")
 	_, err := files.ApplyDiffPatch(ctx, ctx.Repo.Repository, ctx.Doer, &files.ApplyDiffPatchOptions{
 		LastCommitID: parsed.form.LastCommit,
-		OldBranch:    ctx.Repo.BranchName,
-		NewBranch:    parsed.TargetBranchName,
+		OldBranch:    parsed.OldBranchName,
+		NewBranch:    parsed.NewBranchName,
 		Message:      parsed.GetCommitMessage(defaultCommitMessage),
 		Content:      strings.ReplaceAll(parsed.form.Content.Value(), "\r\n", "\n"),
 		Author:       parsed.GitCommitter,
@@ -44,7 +44,7 @@ func NewDiffPatchPost(ctx *context.Context) {
 		err = util.ErrorWrapLocale(err, "repo.editor.fail_to_apply_patch")
 	}
 	if err != nil {
-		editorHandleFileOperationError(ctx, parsed.TargetBranchName, err)
+		editorHandleFileOperationError(ctx, parsed.NewBranchName, err)
 		return
 	}
 	redirectForCommitChoice(ctx, parsed, parsed.form.TreePath)

routers/web/repo/editor_cherry_pick.go

@@ -45,7 +45,7 @@ func CherryPick(ctx *context.Context) {
 
 func CherryPickPost(ctx *context.Context) {
 	fromCommitID := ctx.PathParam("sha")
-	parsed := parseEditorCommitSubmittedForm[*forms.CherryPickForm](ctx)
+	parsed := prepareEditorCommitSubmittedForm[*forms.CherryPickForm](ctx)
 	if ctx.Written() {
 		return
 	}
@@ -53,8 +53,8 @@ func CherryPickPost(ctx *context.Context) {
 	defaultCommitMessage := util.Iif(parsed.form.Revert, ctx.Locale.TrString("repo.commit.revert-header", fromCommitID), ctx.Locale.TrString("repo.commit.cherry-pick-header", fromCommitID))
 	opts := &files.ApplyDiffPatchOptions{
 		LastCommitID: parsed.form.LastCommit,
-		OldBranch:    ctx.Repo.BranchName,
-		NewBranch:    parsed.TargetBranchName,
+		OldBranch:    parsed.OldBranchName,
+		NewBranch:    parsed.NewBranchName,
 		Message:      parsed.GetCommitMessage(defaultCommitMessage),
 		Author:       parsed.GitCommitter,
 		Committer:    parsed.GitCommitter,
@@ -78,7 +78,7 @@ func CherryPickPost(ctx *context.Context) {
 			}
 		}
 		if err != nil {
-			editorHandleFileOperationError(ctx, parsed.TargetBranchName, err)
+			editorHandleFileOperationError(ctx, parsed.NewBranchName, err)
 			return
 		}
 	}

routers/web/repo/editor_fork.go

@@ -0,0 +1,31 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package repo
+
+import (
+	"net/http"
+
+	"code.gitea.io/gitea/modules/templates"
+	"code.gitea.io/gitea/services/context"
+	repo_service "code.gitea.io/gitea/services/repository"
+)
+
+const tplEditorFork templates.TplName = "repo/editor/fork"
+
+func ForkToEdit(ctx *context.Context) {
+	ctx.HTML(http.StatusOK, tplEditorFork)
+}
+
+func ForkToEditPost(ctx *context.Context) {
+	ForkRepoTo(ctx, ctx.Doer, repo_service.ForkRepoOptions{
+		BaseRepo:     ctx.Repo.Repository,
+		Name:         getUniqueRepositoryName(ctx, ctx.Doer.ID, ctx.Repo.Repository.Name),
+		Description:  ctx.Repo.Repository.Description,
+		SingleBranch: ctx.Repo.Repository.DefaultBranch, // maybe we only need the default branch in the fork?
+	})
+	if ctx.Written() {
+		return
+	}
+	ctx.JSONRedirect("") // reload the page, the new fork should be editable now
+}

routers/web/repo/editor_util.go

@@ -11,9 +11,11 @@ import (
 
 	git_model "code.gitea.io/gitea/models/git"
 	repo_model "code.gitea.io/gitea/models/repo"
+	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/log"
+	repo_module "code.gitea.io/gitea/modules/repository"
 	context_service "code.gitea.io/gitea/services/context"
 )
 
@@ -83,3 +85,26 @@ func getParentTreeFields(treePath string) (treeNames, treePaths []string) {
 	}
 	return treeNames, treePaths
 }
+
+// getUniqueRepositoryName Gets a unique repository name for a user
+// It will append a -<num> postfix if the name is already taken
+func getUniqueRepositoryName(ctx context.Context, ownerID int64, name string) string {
+	uniqueName := name
+	for i := 1; i < 1000; i++ {
+		_, err := repo_model.GetRepositoryByName(ctx, ownerID, uniqueName)
+		if err != nil || repo_model.IsErrRepoNotExist(err) {
+			return uniqueName
+		}
+		uniqueName = fmt.Sprintf("%s-%d", name, i)
+		i++
+	}
+	return ""
+}
+
+func editorPushBranchToForkedRepository(ctx context.Context, doer *user_model.User, baseRepo *repo_model.Repository, baseBranchName string, targetRepo *repo_model.Repository, targetBranchName string) error {
+	return git.Push(ctx, baseRepo.RepoPath(), git.PushOptions{
+		Remote: targetRepo.RepoPath(),
+		Branch: baseBranchName + ":" + targetBranchName,
+		Env:    repo_module.PushingEnvironment(doer, targetRepo),
+	})
+}

routers/web/repo/fork.go

@@ -189,17 +189,25 @@ func ForkPost(ctx *context.Context) {
 		}
 	}
 
-	repo, err := repo_service.ForkRepository(ctx, ctx.Doer, ctxUser, repo_service.ForkRepoOptions{
+	repo := ForkRepoTo(ctx, ctxUser, repo_service.ForkRepoOptions{
 		BaseRepo:     forkRepo,
 		Name:         form.RepoName,
 		Description:  form.Description,
 		SingleBranch: form.ForkSingleBranch,
 	})
+	if ctx.Written() {
+		return
+	}
+	ctx.JSONRedirect(ctxUser.HomeLink() + "/" + url.PathEscape(repo.Name))
+}
+
+func ForkRepoTo(ctx *context.Context, owner *user_model.User, forkOpts repo_service.ForkRepoOptions) *repo_model.Repository {
+	repo, err := repo_service.ForkRepository(ctx, ctx.Doer, owner, forkOpts)
 	if err != nil {
 		ctx.Data["Err_RepoName"] = true
 		switch {
 		case repo_model.IsErrReachLimitOfRepo(err):
-			maxCreationLimit := ctxUser.MaxCreationLimit()
+			maxCreationLimit := owner.MaxCreationLimit()
 			msg := ctx.TrN(maxCreationLimit, "repo.form.reach_limit_of_creation_1", "repo.form.reach_limit_of_creation_n", maxCreationLimit)
 			ctx.JSONError(msg)
 		case repo_model.IsErrRepoAlreadyExist(err):
@@ -224,9 +232,7 @@ func ForkPost(ctx *context.Context) {
 		default:
 			ctx.ServerError("ForkPost", err)
 		}
-		return
+		return nil
 	}
-
-	log.Trace("Repository forked[%d]: %s/%s", forkRepo.ID, ctxUser.Name, repo.Name)
-	ctx.JSONRedirect(ctxUser.HomeLink() + "/" + url.PathEscape(repo.Name))
+	return repo
 }

routers/web/repo/view_file.go

@@ -290,7 +290,7 @@ func prepareToRenderFile(ctx *context.Context, entry *git.TreeEntry) {
 
 func prepareToRenderButtons(ctx *context.Context, lfsLock *git_model.LFSLock) {
 	// archived or mirror repository, the buttons should not be shown
-	if ctx.Repo.Repository.IsArchived || !ctx.Repo.Repository.CanEnableEditor() {
+	if !ctx.Repo.Repository.CanEnableEditor() {
 		return
 	}
 
@@ -302,7 +302,9 @@ func prepareToRenderButtons(ctx *context.Context, lfsLock *git_model.LFSLock) {
 	}
 
 	if !ctx.Repo.CanWriteToBranch(ctx, ctx.Doer, ctx.Repo.BranchName) {
+		ctx.Data["CanEditFile"] = true
 		ctx.Data["EditFileTooltip"] = ctx.Tr("repo.editor.fork_before_edit")
+		ctx.Data["CanDeleteFile"] = true
 		ctx.Data["DeleteFileTooltip"] = ctx.Tr("repo.editor.must_have_write_access")
 		return
 	}

routers/web/repo/view_readme.go

@@ -212,7 +212,7 @@ func prepareToRenderReadmeFile(ctx *context.Context, subfolder string, readmeFil
 		ctx.Data["EscapeStatus"], ctx.Data["FileContent"] = charset.EscapeControlHTML(template.HTML(contentEscaped), ctx.Locale)
 	}
 
-	if !fInfo.isLFSFile && ctx.Repo.CanEnableEditor(ctx, ctx.Doer) {
+	if !fInfo.isLFSFile && ctx.Repo.Repository.CanEnableEditor() {
 		ctx.Data["CanEditReadmeFile"] = true
 	}
 }

routers/web/web.go

@@ -1313,23 +1313,35 @@ func registerWebRoutes(m *web.Router) {
 	}, reqSignIn, context.RepoAssignment, context.RepoMustNotBeArchived())
 	// end "/{username}/{reponame}": create or edit issues, pulls, labels, milestones
 
-	m.Group("/{username}/{reponame}", func() { // repo code
+	m.Group("/{username}/{reponame}", func() { // repo code (at least "code reader")
 		m.Group("", func() {
 			m.Group("", func() {
-				m.Post("/_preview/*", repo.DiffPreviewPost)
-				m.Combo("/{editor_action:_edit}/*").Get(repo.EditFile).
-					Post(web.Bind(forms.EditRepoFileForm{}), repo.EditFilePost)
-				m.Combo("/{editor_action:_new}/*").Get(repo.EditFile).
-					Post(web.Bind(forms.EditRepoFileForm{}), repo.EditFilePost)
-				m.Combo("/_delete/*").Get(repo.DeleteFile).
-					Post(web.Bind(forms.DeleteRepoFileForm{}), repo.DeleteFilePost)
-				m.Combo("/_upload/*", repo.MustBeAbleToUpload).Get(repo.UploadFile).
-					Post(web.Bind(forms.UploadRepoFileForm{}), repo.UploadFilePost)
-				m.Combo("/_diffpatch/*").Get(repo.NewDiffPatch).
-					Post(web.Bind(forms.EditRepoFileForm{}), repo.NewDiffPatchPost)
-				m.Combo("/_cherrypick/{sha:([a-f0-9]{7,64})}/*").Get(repo.CherryPick).
-					Post(web.Bind(forms.CherryPickForm{}), repo.CherryPickPost)
-			}, context.RepoRefByType(git.RefTypeBranch), context.CanWriteToBranch(), repo.WebGitOperationCommonData)
+				// "GET" requests only need "code reader" permission, "POST" requests need "code writer" permission.
+				// Because reader can "fork and edit"
+				canWriteToBranch := context.CanWriteToBranch()
+				m.Post("/_preview/*", repo.DiffPreviewPost) // read-only, fine with "code reader"
+				m.Post("/_fork/*", repo.ForkToEditPost)     // read-only, fork to own repo, fine with "code reader"
+
+				// the path params are used in PrepareCommitFormOptions to construct the correct form action URL
+				m.Combo("/{editor_action:_edit}/*").
+					Get(repo.EditFile).
+					Post(web.Bind(forms.EditRepoFileForm{}), canWriteToBranch, repo.EditFilePost)
+				m.Combo("/{editor_action:_new}/*").
+					Get(repo.EditFile).
+					Post(web.Bind(forms.EditRepoFileForm{}), canWriteToBranch, repo.EditFilePost)
+				m.Combo("/{editor_action:_delete}/*").
+					Get(repo.DeleteFile).
+					Post(web.Bind(forms.DeleteRepoFileForm{}), canWriteToBranch, repo.DeleteFilePost)
+				m.Combo("/{editor_action:_upload}/*", repo.MustBeAbleToUpload).
+					Get(repo.UploadFile).
+					Post(web.Bind(forms.UploadRepoFileForm{}), canWriteToBranch, repo.UploadFilePost)
+				m.Combo("/{editor_action:_diffpatch}/*").
+					Get(repo.NewDiffPatch).
+					Post(web.Bind(forms.EditRepoFileForm{}), canWriteToBranch, repo.NewDiffPatchPost)
+				m.Combo("/{editor_action:_cherrypick}/{sha:([a-f0-9]{7,64})}/*").
+					Get(repo.CherryPick).
+					Post(web.Bind(forms.CherryPickForm{}), canWriteToBranch, repo.CherryPickPost)
+			}, context.RepoRefByType(git.RefTypeBranch), repo.WebGitOperationCommonData)
 			m.Group("", func() {
 				m.Post("/upload-file", repo.UploadFileToServer)
 				m.Post("/upload-remove", repo.RemoveUploadFileFromServer)