[O] let org-git-link.el suport Magit related buffers

[stardiviner]

Magit now is the most used tools in Emacs now.

I hope can combine Org-mode links with Magit through `org-git-link.el`.

Current `org-git-link` only support local git file. But it definitely support Magit, like Magit status buffer, Magit log buffer, Magit diff (revision) buffer.

When user is in magit-status/magit-log/magit-revision buffer, get the object under point through Magit API, then construct the org-git-link  link URI to store into Org-mode.

Is there anyone want to or can implement this?