cmd/go: "go get" ignores github default branch

[rogpeppe]

Doing "go get github.com/foo/bar" will always check out
master (assuming no tags are set) even when the default
branch in github is explicitly set to something else.

A possible fix might be to leave vcsGit.tagSyncDefault nil.

[ianlancetaylor]

Comment 1:

Labels changed: added repo-main, release-go1.5.

[frederich]

The cloning works file with Go1.4 and Go1.5 ac45234. Only the branch checkout is wrong.

[frederich]

The default branch feature is only available at Github isn't a Git feature. We can get the default branch information from Github API (https://developer.github.com/v3/repos/#get). Want we really at special Github handling to go get?

[parkr]

This could potentially really slow down go get.

GitHub clones to your default branch, I believe. (Maybe I'm wrong). Just silently fail if no master is found?

[frederich]

Sure it slow down it, and I don't want to have.

I've created a test repo with two branches b and c and no master branch. The branch b is the default Gibhub branch. Cloning over git clone works well. The b branch is checked out. Cloning over go get fails with:

  st% go get -v github.com/frederich/test2_9032
  github.com/frederich/test2_9032 (download)
  # cd /home/jf/src/github.com/frederich/test2_9032; git checkout master
  error: pathspec 'master' did not match any file(s) known to git.
  package github.com/frederich/test2_9032: exit status 1

That's okay, at the moment go get assumes master is always present.

I think we should find the right Git default branch if master is not present. But we should not use the Github API to find the default Github branch.