[GITEA] Allow changing the repo Wiki branch to main

Previously, the repo wiki was hardcoded to use `master` as its branch,
this change makes it possible to use `main` (or something else, governed
by `[repository].DEFAULT_BRANCH`, a setting that already exists and
defaults to `main`).

The way it is done is that a new column is added to the `repository`
table: `wiki_branch`. The migration will make existing repositories
default to `master`, for compatibility's sake, even if they don't have a
Wiki (because it's easier to do that). Newly created repositories will
default to `[repository].DEFAULT_BRANCH` instead.

The Wiki service was updated to use the branch name stored in the
database, and fall back to the default if it is empty.

Old repositories with Wikis using the older `master` branch will have
the option to do a one-time transition to `main`, available via the
repository settings in the "Danger Zone". This option will only be
available for repositories that have the internal wiki enabled, it is
not empty, and the wiki branch is not `[repository].DEFAULT_BRANCH`.

When migrating a repository with a Wiki, Forgejo will use the same
branch name for the wiki as the source repository did. If that's not the
same as the default, the option to normalize it will be available after
the migration's done.

Additionally, the `/api/v1/{owner}/{repo}` endpoint was updated: it will
now include the wiki branch name in `GET` requests, and allow changing
the wiki branch via `PATCH`.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>
(cherry picked from commit d87c526d2a313fa45093ab49b78bb30322b33298)

3 files changed, 29 insertions, 1 deletions

diff --git a/modules/context/repo.go b/modules/context/repo.go
index 75ebfec705..b48f6ded26 100644
--- a/modules/context/repo.go
+++ b/modules/context/repo.go
@@ -400,6 +400,7 @@ func repoAssignment(ctx *Context, repo *repo_model.Repository) {
 	ctx.Data["PushMirrors"] = pushMirrors
 	ctx.Data["RepoName"] = ctx.Repo.Repository.Name
 	ctx.Data["IsEmptyRepo"] = ctx.Repo.Repository.IsEmpty
+	ctx.Data["DefaultWikiBranchName"] = setting.Repository.DefaultBranch
 }
 
 // RepoIDAssignment returns a handler which assigns the repo to the context.
diff --git a/modules/repository/repo.go b/modules/repository/repo.go
index fc3af04071..65b50b2e45 100644
--- a/modules/repository/repo.go
+++ b/modules/repository/repo.go
@@ -1,4 +1,5 @@
 // Copyright 2019 The Gitea Authors. All rights reserved.
+// Copyright 2024 The Forgejo Authors c/o Codeberg e.V.. All rights reserved.
 // SPDX-License-Identifier: MIT
 
 package repository
@@ -99,7 +100,6 @@ func MigrateRepositoryGitData(ctx context.Context, u *user_model.User,
 				Mirror:        true,
 				Quiet:         true,
 				Timeout:       migrateTimeout,
-				Branch:        "master",
 				SkipTLSVerify: setting.Migrations.SkipTLSVerify,
 			}); err != nil {
 				log.Warn("Clone wiki: %v", err)
@@ -107,6 +107,30 @@ func MigrateRepositoryGitData(ctx context.Context, u *user_model.User,
 					return repo, fmt.Errorf("Failed to remove %s: %w", wikiPath, err)
 				}
 			} else {
+				// Figure out the branch of the wiki we just cloned. We assume
+				// that the default branch is to be used, and we'll use the same
+				// name as the source.
+				gitRepo, err := git.OpenRepository(ctx, wikiPath)
+				if err != nil {
+					log.Warn("Failed to open wiki repository during migration: %v", err)
+					if err := util.RemoveAll(wikiPath); err != nil {
+						return repo, fmt.Errorf("Failed to remove %s: %w", wikiPath, err)
+					}
+					return repo, err
+				}
+				defer gitRepo.Close()
+
+				branch, err := gitRepo.GetDefaultBranch()
+				if err != nil {
+					log.Warn("Failed to get the default branch of a migrated wiki repo: %v", err)
+					if err := util.RemoveAll(wikiPath); err != nil {
+						return repo, fmt.Errorf("Failed to remove %s: %w", wikiPath, err)
+					}
+
+					return repo, err
+				}
+				repo.WikiBranch = branch
+
 				if err := git.WriteCommitGraph(ctx, wikiPath); err != nil {
 					return repo, err
 				}
diff --git a/modules/structs/repo.go b/modules/structs/repo.go
index 51e175fba8..483723b575 100644
--- a/modules/structs/repo.go
+++ b/modules/structs/repo.go
@@ -88,6 +88,7 @@ type Repository struct {
 	ExternalTracker               *ExternalTracker `json:"external_tracker,omitempty"`
 	HasWiki                       bool             `json:"has_wiki"`
 	ExternalWiki                  *ExternalWiki    `json:"external_wiki,omitempty"`
+	WikiBranch                    string           `json:"wiki_branch,omitempty"`
 	HasPullRequests               bool             `json:"has_pull_requests"`
 	HasProjects                   bool             `json:"has_projects"`
 	HasReleases                   bool             `json:"has_releases"`
@@ -175,6 +176,8 @@ type EditRepoOption struct {
 	ExternalWiki *ExternalWiki `json:"external_wiki,omitempty"`
 	// sets the default branch for this repository.
 	DefaultBranch *string `json:"default_branch,omitempty"`
+	// sets the branch used for this repository's wiki.
+	WikiBranch *string `json:"wiki_branch,omitempty"`
 	// either `true` to allow pull requests, or `false` to prevent pull request.
 	HasPullRequests *bool `json:"has_pull_requests,omitempty"`
 	// either `true` to enable project unit, or `false` to disable them.