Support for GitLab subgroups

[rozwad]

A quick and dirty prototype workaround to address issue #259.

As the install_gitlab seems to not support (yet) subdirectories, the workaround is based on the subdir variable. However in case a repo is inside a subgroup there is a mismatch – subdir corresponds to a repository, and repo to a subgroup (result of the general parsing rules in parse_repo_spec). How about fixing that mismatch with a new dedicated parse_repo_gitlab function?

[jimhester]

Are you actually getting a trailing slash in the subdirectory or just being cautious? In general I would consider specs with a trailing slash to be invalid input, and actually it seems parse_git_repo() strips them anyway, so you can remove the gsub here and below I think.

> parse_git_repo("foo/bar/baz/")
$username
[1] "foo"

$repo
[1] "bar"

$subdir
[1] "baz"

[jimhester]

Oh now that I look at this again this handles the case when subdir is empty. I think a better approach is to use paste0(c(x$username, x$repo, x$subdir), collapse = "/")

[robertdj]

I am also missing this functionality of installing packages from a path with three levels (not sure if it is a subgroup or subdirectory).

Having tried out this branch I still run into problems.

As far as I can see install_gitlab makes three calls to get the repository in path/to/repo:

• One to get DESCRIPTION: https://gitlab.foo.com/path/to/repo/raw/master/DESCRIPTION?private_token=token
• One to get some metadata about the repo using a URL encoded path/to/repo: https://gitlab.foo.com/api/v4/projects/path%2Fto%2Frepo/repository/commits/master?private_token=token
• One to get the repository as a tar.gz file: https://gitlab.foo.com/path/to/repo/repository/archive.tar.gz?ref=master?private_token=token

The first two works for me, but the last one fails.
According to GitLab's documentation the last call should also be different -- using the same form as the second call:
https://gitlab.foo.com/api/v4/projects/path%2Fto%2Frepo/repository/archive.tar.gz?ref=master&private_token=

With this change it works for me.
@rozwad : Does this also work for you?

[kevinushey]

IMHO we should avoid overloading the meaning of subdir (since a subgroup and folder within a repository are different things) and instead consider how to handle sub-directories and sub-groups.

I think it would be better to augment the parser so that there's a way to parse sub-directories and sub-groups separately (either globally or just a GitLab-only parser).