Add test for GetTags

[strk]

See the need for it in go-gitea/gitea#1133 (comment)

[strk]

@lafriks this repository has no tags, are you in a position to add any ? So we can test more easily...

[lafriks]

I could but I have no idea what version should be added here :)

[strk]

How about adding a tag at the fork point from gogs ?

[lunny]

@strk release/v0.9 in gitea repository.