codereview: fix hg change on Windows
hg change fails on Windows with 'No valid patches found in output from hg diff'.
R=rsc
CC=golang-dev
https://golang.org/cl/4006043
diff --git a/lib/codereview/codereview.py b/lib/codereview/codereview.py
index 0a345d8..ab8415e 100644
--- a/lib/codereview/codereview.py
+++ b/lib/codereview/codereview.py
@@ -2607,7 +2607,7 @@
self.base_rev = self.options.revision
else:
mqparent, err = RunShellWithReturnCode(['hg', 'log', '--rev', 'qparent', '--template={node}'])
- if not err:
+ if not err and mqparent != "":
self.base_rev = mqparent
else:
self.base_rev = RunShell(["hg", "parents", "-q"]).split(':')[1].strip()
