Generated manifest.json removes git tags

[hadess]

Given this module:

        {
            "name": "librest",
            "sources": [
                {
                    "type": "git",
                    "url": "https://gitlab.gnome.org/GNOME/librest.git",
                    "tag": "0.8.1"
                }
            ]
        },

flatpak-builder will transform it to:

    {   
      "name" : "librest",
      "sources" : [ 
        {
          "url" : "https://gitlab.gnome.org/GNOME/librest.git",
          "commit" : "bd33ade80080687e49b87329bf587e966b859bbb",
          "type" : "git"
        }
      ]   
    },  

It would be very useful if the "tag" property was kept, as it's more human-readable than just the commit itself, and having the commit fixes the problem of tags being tampered with (maliciously or not) in some cases.

So I'd expect:

                    "url": "https://gitlab.gnome.org/GNOME/librest.git",
                    "tag": "0.8.1"

to be transformed to:

          "url" : "https://gitlab.gnome.org/GNOME/librest.git",
          "commit" : "bd33ade80080687e49b87329bf587e966b859bbb",
          "tag": "0.8.1"