[banshee] HACKING: add some info about metadata in git commit messages

[Andrés Aragoneses <aaragoneses src gnome org>]

commit 31e2b4f75a87248096fc04cba6228e6182a02a3f
Author: Andrés G. Aragoneses <knocte gmail com>
Date:   Tue Jul 22 14:27:01 2014 +0200

    HACKING: add some info about metadata in git commit messages
    
    The first item in this list is actually related to git commit
    messages, but next three are actually consequences of the first
    (assumptions we've had over the years which were not written before).

 HACKING |   20 +++++++++++++++++++-
 1 files changed, 19 insertions(+), 1 deletions(-)
---
diff --git a/HACKING b/HACKING
index 9ec3df2..8613c66 100644
--- a/HACKING
+++ b/HACKING
@@ -10,7 +10,25 @@ formatting details of this message are described here:
 
   http://live.gnome.org/Git/CommitMessages
 
-Please review these guidelines separate to this document.
+Please review these guidelines separate to this document, and take in account
+these policies on top:
+
+  1. Unlike many other open-source projects, we don't use the git tagging
+     'Signed-off-by' to refer as a licencing statement of a contribution,
+     rather we use it as 'Reviewed by this maintainer' metadata.
+
+  2. As a consequence of the above, the choice of licencing attribution
+     is implicit: by contributing a patch to the Banshee project you are
+     automatically accepting to follow the same licence as the project
+     itself (see our COPYING file) unless stated on the contrary.
+
+  3. When a contributed patch contains new files, please include licence
+     headers in each of them, in the same way the rest of the files of
+     the projects already have.
+
+  4. It's recommended that you add yourself (or your company) to the list
+     of the copyright owners of a file if you're modifying a considerable
+     proportion of it.
 
 
 C# Coding Style Guidelines