Dump github/gitlab/gitea repository data to a local directory and restore to gitea (#12244)

* Dump github/gitlab repository data to a local directory

* Fix lint

* Adjust directory structure

* Allow migration special units

* Allow migration ignore release assets

* Fix lint

* Add restore repository

* stage the changes

* Merge

* Fix lint

* Update the interface

* Add some restore methods

* Finish restore

* Add comments

* Fix restore

* Add a token flag

* Fix bug

* Fix test

* Fix test

* Fix bug

* Fix bug

* Fix lint

* Fix restore

* refactor downloader

* fmt

* Fix bug isEnd detection on getIssues

* Refactor maxPerPage

* Remove unused codes

* Remove unused codes

* Fix bug

* Fix restore

* Fix dump

* Uploader should not depend downloader

* use release attachment name but not id

* Fix restore bug

* Fix lint

* Fix restore bug

* Add a method of DownloadFunc for base.Release to make uploader not depend on downloader

* fix Release yml marshal

* Fix trace information

* Fix bug when dump & restore

* Save relative path on yml file

* Fix bug

* Use relative path

* Update docs

* Use git service string but not int

* Recognize clone addr to service type

modules/migrations/error.go

@@ -14,6 +14,9 @@ import (
 var (
 	// ErrNotSupported returns the error not supported
 	ErrNotSupported = errors.New("not supported")
+
+	// ErrRepoNotCreated returns the error that repository not created
+	ErrRepoNotCreated = errors.New("repository is not created yet")
 )
 
 // IsRateLimitError returns true if the err is github.RateLimitError