pager: set some environment variables if they're not set Git did this already [1] [2]. We want this behavior too [3]. This provides a better default user experience (like, supporting colors) if users have things like "PAGER=less" set, which is not uncommon. The environment variables are provided by a method so extensions can override them on demand. [1]: https://github.com/git/git/blob/6a5ff7acb5965718cc7016c0ab6c601454fd7cde/pager.c#L87 [2]: https://github.com/git/git/blob/6a5ff7acb5965718cc7016c0ab6c601454fd7cde/Makefile#L1545 [3]: https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-March/094780.html

--- a/mercurial/rcutil.py	Thu Apr 13 14:48:18 2017 -0400
+++ b/mercurial/rcutil.py	Thu Apr 13 08:27:19 2017 -0700
@@ -90,3 +90,9 @@
         _rccomponents.append(envrc)
         _rccomponents.extend(normpaths(userrcpath()))
     return _rccomponents
+
+def defaultpagerenv():
+    '''return a dict of default environment variables and their values,
+    intended to be set before starting a pager.
+    '''
+    return {'LESS': 'FRX', 'LV': '-c'}