Support Bitbucket Data Center (the self-managed Bitbucket)

[eckdanny]

Interest in supporting Bitbucket Data Center (the self-managed Atlassian product that [AFAIK] is API-compatible with Bitbucket Cloud?) Same impl probably applicable for GitLab Cloud/Self-Managed.

I need to do simple scaffolding á lá degit (shallow-clone/sparse-checkout (git), or yank from a zip/tar/tgz archive (http), don't care). State of private repo support from README confused me at first, but after reviewing #29 I thought maybe Bitbucket Data Center repo URLs might work. Realized of course those could be anything so parse can't make that determination.

degit is pretty slick. I'll probably have to pwsh/bash/node script a sol'n for my immediate needs (no cache, modes, or tests like degit). But if there's an interest in adding something like a ProviderCapabilities/ProviderId to capture the relationship Bitbucket and GitLab have with Cloud/Self-Managed API compatibility, I'd be interested in working on that.

Related: #20, #29