[PATCH 1 of 3] revset: short docstring for checkstatus

[Jordi Gutiérrez Hermoso]

# HG changeset patch
# User Jordi Gutiérrez Hermoso <jordigh at octave.org>
# Date 1554489052 14400
#      Fri Apr 05 14:30:52 2019 -0400
# Node ID 9fcb915a73b83547921aaa13584c88cb99c6aee7
# Parent  a975821d0938615b8cb235f12cc6461a42dcfbd8
revset: short docstring for checkstatus

This is where all the action happens for the status-related revsets,
and a little documentation doesn't hurt.

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -598,6 +598,12 @@ def bundle(repo, subset, x):
     return subset & bundlerevs
 
 def checkstatus(repo, subset, pat, field):
+    """Helper for status-related revsets (adds, removes, modifies,
+    renames, copies). The field parameter says which kind is desired:
+    0: modified
+    1: added
+    2: removed
+    """
     hasset = matchmod.patkind(pat) == 'set'
 
     mcache = [None]