Do a git checkout of the target repo:
git clone https://skia.googlesource.com/git-master-skia
Then point to that directory as the url handed to androidingest as the --repo_url. This will give you up to date commits, but also doesn't require write access to the origin repo. You will probably have to be on a non-master branch in the checkout so that the copy androidingest builds can push back to it.
The process of creating git commits to mirror buildids has too high on an error rate.
Make sure the git-cookie-authdaemon is running and that it is populating the git cookie at /home/default/.git-credentials-cache/cookie.
Also check the logs for the exact operation in the process that is failing.