refactor: clean up git repo and model migration packages (#38564)

enable the golangci depguard lint rule: deny "models" and its sub
packages in "modelmigration" package.

modules/git/gitrepo/dbrepo.go

@@ -0,0 +1,24 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package gitrepo
+
+import "strings"
+
+func RepoCodeGitRepoRelativePath(ownerName, repoName string) string {
+	return strings.ToLower(ownerName) + "/" + strings.ToLower(repoName) + ".git"
+}
+
+func RepoWikiGitRepoRelativePath(ownerName, repoName string) string {
+	return strings.ToLower(ownerName) + "/" + strings.ToLower(repoName) + ".wiki.git"
+}
+
+// CodeRepoByName returns an unmanaged repository facade for the code repository of the given owner and repository name.
+// Usually it is used for migration fixes or repository adoption/creation/rename/transfer.
+func CodeRepoByName(ownerName, repoName string) RepositoryFacade {
+	return RepositoryUnmanaged(RepoCodeGitRepoRelativePath(ownerName, repoName))
+}
+
+func WikiRepoByName(ownerName, repoName string) RepositoryFacade {
+	return RepositoryUnmanaged(RepoWikiGitRepoRelativePath(ownerName, repoName))
+}

modules/git/gitrepo/gitrepo.go

@@ -0,0 +1,102 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package gitrepo
+
+import (
+	"path/filepath"
+	"sync/atomic"
+
+	"gitea.dev/modules/setting"
+)
+
+type RepositoryFacade interface {
+	// GitRepoManagedID returns a "managed id", which should be a cache-key-friendly string.
+	// e.g.: ID with prefix&suffix or UUID
+	GitRepoManagedID() string
+
+	// GitRepoLocation returns the location for the git repository.
+	// * relative path: will be converted to an absolute path by setting.RepoRootPath
+	// * absolute path: will be used as-is
+	// * in the future: maybe URI for more flexible definitions
+	GitRepoLocation() string
+
+	LogString() string
+}
+
+// RepoLocalPath returns an absolute path for a RepositoryFacade.
+// TODO: most of the calls to this function should be replaced with a "Repo FS" in the future
+// to handle file accesses in the git repo (e.g.: read, write, list, remove).
+func RepoLocalPath(repo RepositoryFacade) string {
+	repoLoc := repo.GitRepoLocation()
+	if filepath.IsAbs(repoLoc) {
+		return repoLoc
+	}
+	if setting.RepoRootPath == "" {
+		panic("repo root path is not initialized")
+	}
+	// the repo root path and the repo loc should all have been cleaned, so we can safely join them together
+	return setting.RepoRootPath + string(filepath.Separator) + filepath.FromSlash(repoLoc)
+}
+
+func repoLogNameByLocation(loc string) string {
+	t := filepath.FromSlash(loc)
+	// hide the parent paths, then the name should be safe for end users
+	return ".../" + filepath.Base(filepath.Dir(t)) + "/" + filepath.Base(t)
+}
+
+type repositoryUnmanaged struct {
+	loc     string
+	logName atomic.Pointer[string]
+}
+
+func (r *repositoryUnmanaged) LogString() string {
+	s := r.logName.Load()
+	if s == nil {
+		s = new(repoLogNameByLocation(r.loc))
+		r.logName.Store(s)
+	}
+	return *s
+}
+
+func (r *repositoryUnmanaged) GitRepoManagedID() string {
+	panic("this repo is not managed by Gitea, can't be used in this managed context")
+}
+
+func (r *repositoryUnmanaged) GitRepoLocation() string {
+	return r.loc
+}
+
+// RepositoryUnmanaged returns a RepositoryFacade for a repository that might not be managed by Gitea.
+// If the path is not absolute, then it is relative to setting.RepoRootPath
+// This function is mainly for maintaining the owner's repo when the repo is not managed yet.
+// e.g.: init, clone, transfer, rename, adopt, etc., and temp repo creation and modification.
+func RepositoryUnmanaged(s string) RepositoryFacade {
+	return &repositoryUnmanaged{loc: filepath.Clean(s)}
+}
+
+type repositoryManaged struct {
+	id, loc string
+	logName atomic.Pointer[string]
+}
+
+func (r *repositoryManaged) LogString() string {
+	s := r.logName.Load()
+	if s == nil {
+		s = new(repoLogNameByLocation(r.loc))
+		r.logName.Store(s)
+	}
+	return *s
+}
+
+func (r *repositoryManaged) GitRepoManagedID() string {
+	return r.id
+}
+
+func (r *repositoryManaged) GitRepoLocation() string {
+	return r.loc
+}
+
+func RepositoryManaged(id, loc string) RepositoryFacade {
+	return &repositoryManaged{id: id, loc: filepath.Clean(loc)}
+}