cannot create pull request for self-hosted gitlab

[enekofb]

At the back of #126

We are doing e2e test for pull request promotions for gitlab.

We have found that when using weaveworks hosted instances, we cannot create pull requests
#126 (comment)

with the following error

{"level":"error","ts":"2022-12-22T15:22:34.002Z","logger":"promotion.handler","msg":"error promoting application","error":"failed to create PR: failed to retrieve repository: ","stacktrace":"github.com/weaveworks/pipeline-controller/server.DefaultPromotionHandler.ServeHTTP\n\t/workspace/server/promotion_handler.go:116\nnet/http.StripPrefix.func1\n\t/usr/local/go/src/net/http/server.go:2152\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2109\nnet/http.(*ServeMux).ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2487\nnet/http.serverHandler.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2947\nnet/http.(*conn).serve\n\t/usr/local/go/src/net/http/server.go:1991"}

This ticket to address this bug. you could use the following gitlab instance https://gitlab.git.dev.weave.works or the repo
https://gitlab.git.dev.weave.works/pipeline-controller/pipeline-controller-e2e/

Acceptance Criteria

• fixed the issue
• enabled the gitlab scenario in e2e

[enekofb]

It seems to be that there is a bug in gitlab go-git-providers. raised the following issues

fluxcd/go-git-providers#175
fluxcd/go-git-providers#176