sparse: expand module docstring
Clarify lack of BC guarantees. And say a bit more about the extension.
--- a/hgext/sparse.py Sat Jul 01 10:43:29 2017 -0700
+++ b/hgext/sparse.py Sat Jul 01 10:36:03 2017 -0700
@@ -6,6 +6,17 @@
# GNU General Public License version 2 or any later version.
"""allow sparse checkouts of the working directory (EXPERIMENTAL)
+
+(This extension is not yet protected by backwards compatibility
+guarantees. Any aspect may break in future releases until this
+notice is removed.)
+
+This extension allows the working directory to only consist of a
+subset of files for the revision. This allows specific files or
+directories to be explicitly included or excluded. Many repository
+operations have performance proportional to the number of files in
+the working directory. So only realizing a subset of files in the
+working directory can improve performance.
"""
from __future__ import absolute_import