Add support for GitLab tags

[sum01]

API call to get a list of tags: https://WEBSITEHERE/api/v4/projects/USERNAMEHERE%2FREPONAMEHERE/repository/tags.

Notes:

• So for https://gitlab.gnome.org WEBSITEHERE would be gitlab.gnome.org, but free hosting on gitlab is merely gitlab.com
• The resulting tag_list[0].name will be the newest tag's version/name.
• There are no seperate "releases" like Github, everything is under tags.
• USERNAMEHERE%2FREPONAMEHERE is the username and reponame url-encoded, so that %2F is a forward-slash. It's required that they be url-encoded, so special characters will need to be delt with.

The WEBSITEHERE part would be needed to be stripped from the source target.

For example, getting a tar.gz from https://gitlab.gnome.org/GNOME/nautilus looks like https://gitlab.gnome.org/GNOME/nautilus/-/archive/3.28.1/nautilus-3.28.1.tar.gz, and https://gitlab.com/gitlab-org/gitlab-ce would be https://gitlab.com/gitlab-org/gitlab-ce/-/archive/v11.0.0-rc7/gitlab-ce-v11.0.0-rc7.tar.gz

The prefixed website doesn't change when targetting other sources, such as binaries, bzip's, etc.

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Example calls

Source	API call
https://gitlab.com/gitlab-org/gitlab-ce	https://gitlab.com/api/v4/projects/gitlab-org%2Fgitlab-ce/repository/tags
https://gitlab.gnome.org/GNOME/nautilus	https://gitlab.gnome.org/api/v4/projects/GNOME%2Fnautilus/repository/tags

[sum01]

I'm looking at the code & I'm curious if there's any recommendations for contributing? Like "use go imports" or "follow xyz styleguide", etc?

[sum01]

I'm working on it, although I'm not very experienced with Go so it might take a day or two before I push a PR. I'm just using Goimports to format code, so I hope that's fine.

EDIT: Actually got it working quite quickly, I just need to write the tests.

[carlosal1015]

Hi @simon04, I do not know if is working how I am expecting, could you check please?

$ aur-out-of-date -pkg alberta
             [UNKNOWN] [alberta][3.0.3-2] No GitLab release found for gitlab.mathematik.uni-stuttgart.de/ians-nmh/alberta on https://gitlab.mathematik.uni-stuttgart.de/api/v4/projects/ians-nmh%2Falberta/repository/tags