[PATCH] largefiles: document behavior of caching largefiles for new heads

[natosha at unity3d.com]

# HG changeset patch
# User Na'Tosha Bard <natosha at unity3d.com>
# Date 1360423546 0
# Node ID f8d2ba43dbdbc0afad50b66dd4c3c1da28ce6d65
# Parent  97761496c65ae836d6b0983a3f48959dd3112364
largefiles: document behavior of caching largefiles for new heads

diff -r 97761496c65a -r f8d2ba43dbdb hgext/largefiles/__init__.py
--- a/hgext/largefiles/__init__.py	Fri Feb 08 22:42:07 2013 +0000
+++ b/hgext/largefiles/__init__.py	Sat Feb 09 15:25:46 2013 +0000
@@ -41,11 +41,20 @@
 enabled for this to work.
 
 When you pull a changeset that affects largefiles from a remote
-repository, Mercurial behaves as normal. However, when you update to
-such a revision, any largefiles needed by that revision are downloaded
-and cached (if they have never been downloaded before). This means
-that network access may be required to update to changesets you have
-not previously updated to.
+repository, the largefiles for the changeset usually won't be
+pulled down until you update to the revision (there is one exception
+to this case).  However, when you update to such a revision, any
+largefiles needed by that revision are downloaded and cached (if
+they have never been downloaded before).  This means that network
+access may be required to update to changesets you have no
+previously updated to.
+
+The one exception to the "largefiles won't be pulled until you update
+to a revision that changes them" rule is when you pull new heads.
+Because you could be pulling new heads (that you may later want to
+merge with) from a non-default location (that Mercurial won't know
+about later), when you pull new heads, largefiles revisions for those
+heads are downloaded and cached locally.
 
 If you already have large files tracked by Mercurial without the
 largefiles extension, you will need to convert your repository in