fix forge api base url construction

[pigam]

Fix forge api API base URL selection for self-hosted forge instances.

forge api previously selected the API root using domain-name substring checks, for example by looking for gitlab in the hostname. This breaks self-hosted instances whose domain does not include the expected forge-specific substring.

Closes #140

Changes

• Extract API base URL selection into apiBaseURL.
• Resolve the API root from:
  1. explicit --forge-type
  2. configured domain type
  3. known-domain defaults
  4. existing hostname heuristics as fallback
• Add unit tests for:
  • known domains
  • unknown domains with explicit forge type
  • unknown domains with configured forge type
  • unknown domains without type information

[pigam]

Further analysis : the api base url is a property of a forge.

resolve.Repo returns a Forge, but the result is ignored here.

_, owner, repoName, domain, err := resolve.Repo(flagRepo, flagForgeType)
^
# forge !

Normal, as the Forge interface has not yet a way to return this information.

I think a cleaner solution would be to add APIBaseURL to the Forge interface, but this would force the change on all actual forges backend.

An opinion ?

[andrew]

Agreed, the API base URL belongs to the resolved forge. I’d use a small companion interface such as APIBaseURLProvider rather than changing Forge, so external implementations do not break. Then forge api can use the resolved backend directly, including types found by probing and GitHub Enterprise’s /api/v3 URL.