Add support for migrating from Gitlab (#9084)

* First stab at a Gitlab migrations interface.

* Modify JS to show migration for Gitlab

* Properly strip out #gitlab tag from repo name

* Working Gitlab migrations!
Still need to figure out how to hide tokens/etc from showing up in opts.CloneAddr

* Try #2 at trying to hide credentials.
CloneAddr was being used as OriginalURL.
Now passing OriginalURL through from the form and saving it.

* Add go-gitlab dependency

* Vendor go-gitlab

* Use gitlab.BasicAuthClient
Correct CloneURL.
This should be functioning!
Previous commits fixed "Migrated from"
from including the migration credentials.

* Replaced repoPath with repoID globally.
RepoID is grabbed in NewGitlabDownloader

* Logging touchup

* Properly set private repo status.
Properly set milestone deadline time.
Consistently use Gitlab username for 'Name'.

* Add go-gitlab vendor cache

* Fix PR migrations:
- Count of issues is kept to set a non-conflicting PR.ID
- Bool is used to tell whether to fetch Issue or PR comments

* Ensure merged PRs are closed and set with the proper time

* Remove copyright and some commented code

* Rip out '#gitlab' based self-hosted Gitlab support

* Hide given credentials for migrated repos.

CloneAddr was being saved as OriginalURL.

Now passing OriginalURL through from the form and
saving it in it's place

* Use asset.URL directly, no point in parsing.
Opened PRs should fall through to false.

* Fix importing Milestones.
Allow importing using Personal Tokens or anonymous access.

* Fix Gitlab Milestone migration if DueDate isn't set

* Empty Milestone due dates properly return nil, not zero time

* Add GITLAB_READ_TOKEN to drone unit-test step

* Add working gitlab_test.go.
A Personal Access Token, given in env variable GITLAB_READ_TOKEN
is required to run the test.

* Fix linting issues

* Add modified JS files

* Remove pre-build JS files

* Only merged PRs are marged as merged/closed

* Test topics

* Skip test if gitlab is inaccessible

* Grab personal token from username, not password.
Matches Github migration implementation

* Add SetContext() to GitlabDownloader.

* Checking Updated field in Issues.

* Actually fetch Issue Updated time from Gitlab

* Add Gitlab migration GetReviews() stub

* Fix Patch and Clone URLs

* check Updated too

* fix mod

* make vendor with go1.14

Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

go.mod

@@ -104,6 +104,7 @@ require (
 	github.com/unknwon/i18n v0.0.0-20190805065654-5c6446a380b6
 	github.com/unknwon/paginater v0.0.0-20151104151617-7748a72e0141
 	github.com/urfave/cli v1.20.0
+	github.com/xanzy/go-gitlab v0.22.1
 	github.com/yohcop/openid-go v0.0.0-20160914080427-2c050d2dae53
 	github.com/yuin/goldmark v1.1.25
 	github.com/yuin/goldmark-meta v0.0.0-20191126180153-f0638e958b60