Merge branch 'mz/doc-notes-are-not-anchors'

Objects that lost references can be pruned away, even when they
have notes attached to it (and these notes will become dangling,
which in turn can be pruned with "git notes prune").  This has been
clarified in the documentation.

* mz/doc-notes-are-not-anchors:
  docs: clarify that refs/notes/ do not keep the attached objects alive

Documentation/git-gc.txt

@@ -117,12 +117,14 @@ NOTES
 'git gc' tries very hard not to delete objects that are referenced
 anywhere in your repository. In particular, it will keep not only
 objects referenced by your current set of branches and tags, but also
-objects referenced by the index, remote-tracking branches, notes saved
+objects referenced by the index, remote-tracking branches, reflogs
-by 'git notes' under refs/notes/, reflogs (which may reference commits
+(which may reference commits in branches that were later amended or
-in branches that were later amended or rewound), and anything else in
+rewound), and anything else in the refs/* namespace. Note that a note
-the refs/* namespace.  If you are expecting some objects to be deleted
+(of the kind created by 'git notes') attached to an object does not
-and they aren't, check all of those locations and decide whether it
+contribute in keeping the object alive. If you are expecting some
-makes sense in your case to remove those references.
+objects to be deleted and they aren't, check all of those locations
+and decide whether it makes sense in your case to remove those
+references.
 
 On the other hand, when 'git gc' runs concurrently with another process,
 there is a risk of it deleting an object that the other process is using