# HG changeset patch
# User Yuya Nishihara <yuya@tcha.org>
# Date 1474540902 -32400
# Node ID d67bcfc0041f796e6a028cdd7d0dea3bf60f4ec7
# Parent  d36eda8896ccd5157e76610275f54dd1e4599187
revset: make follow() accept empty startrev

This is the same behavior as ancestors(emptyset).

diff -r d36eda8896cc -r d67bcfc0041f mercurial/revset.py
--- a/mercurial/revset.py	Thu Sep 22 19:40:07 2016 +0900
+++ b/mercurial/revset.py	Thu Sep 22 19:41:42 2016 +0900
@@ -913,9 +913,6 @@
     revs = None
     if 'startrev' in args:
         revs = getset(repo, fullreposet(repo), args['startrev'])
-        if not revs:
-            raise error.RepoLookupError(
-                _("%s expected at least one starting revision") % name)
     if 'file' in args:
         x = getstring(args['file'], _("%s expected a pattern") % name)
         if revs is None:
diff -r d36eda8896cc -r d67bcfc0041f tests/test-log.t
--- a/tests/test-log.t	Thu Sep 22 19:40:07 2016 +0900
+++ b/tests/test-log.t	Thu Sep 22 19:41:42 2016 +0900
@@ -742,8 +742,6 @@
 follow files starting from empty revision:
 
   $ hg log -T '{rev}: {files}\n' -r "follow('glob:*', startrev=.-.)"
-  abort: follow expected at least one starting revision!
-  [255]
 
 follow starting from revisions: