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/git.go

@@ -6,7 +6,6 @@ package migrations
 
 import (
 	"context"
-	"io"
 
 	"code.gitea.io/gitea/modules/migrations/base"
 )
@@ -65,11 +64,6 @@ func (g *PlainGitDownloader) GetReleases() ([]*base.Release, error) {
 	return nil, ErrNotSupported
 }
 
-// GetAsset returns an asset
-func (g *PlainGitDownloader) GetAsset(_ string, _, _ int64) (io.ReadCloser, error) {
-	return nil, ErrNotSupported
-}
-
 // GetIssues returns issues according page and perPage
 func (g *PlainGitDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, error) {
 	return nil, false, ErrNotSupported