Clean up install_github parameters pull and branch

[krlmlr]

The ref and pull parameters are mutually exclusive, and the branch parameter has been deprecated. The latter two should be removed, and the ref parameter should now also accept functions.

If ref is a function, it will be called with a named list that contains all other parameters (after parsing with github_parse_path and obtaining access tokens), and return an updated version of this list. Implementation and usage examples:

github_pull_request <- function(pull) {
  force(pull)
  function(param) {
    pullinfo <- github_pull_info(param$repo, param$username, param$pull)
    param$username <- pullinfo$username
    param$ref <- pullinfo$ref
    param
  }
}

install_github("devtools", ref = github_pull_request(475))

github_pull_request <- function(pull) {
  force(pull)
  function(param) {
    pullinfo <- github_pull_info(param$repo, param$username, param$pull)
    param$username <- pullinfo$username
    param$ref <- pullinfo$ref
    param
  }
}

github_release <- function(pos = 1, pre_release = TRUE) {
  force(pos)
  force(pre_release)
  function(param) {
    param$ref <- ...
    param
  }
}

install_github("devtools", github_release())

This would allow for a cleaner implementation of #350.

Usage of the deprecated parameters pull and branch can be detected by looking at ....

Thoughts?

[hadley]

I'd prefer to use some simple S3 dispatch.

[krlmlr]

Do you mean something like this:

github_ref <- function(x) UseMethod("github_ref")
github_ref.default <- function(x) list(ref=x)
github_ref.pull <- function(x) {
  list(repo=xxx, username=yyy, ref=zzz)
}
github_pull <- function(pull) structure(pull, class="pull")

# in github_get_conn:
ref_params <- github_ref(ref)
params[names(ref_params)] <- ref_params

?

[hadley]

Yes, exactly, except I'd write the last bit as ref_params <- modifyList(params, github_ref(ref))

[krlmlr]

This implementation seems to work for me.

[hadley]

Won't this always be false?

[krlmlr]

Not if an explicit pull = xxx is passed to install_github -- it will be captured by ... and assigned to pull in the call to install_github_single.

[hadley]

Oh I see - missed the separation of the functions in the diff.

[krlmlr]

Should be okay now.

[hadley]

Thanks!