templater: allow piping generator-type function output to filters Template functions use "yield"s assuming that the result will be combined into a string, which means both "f -> str" and "f -> generator" should behave in the same way. Before this patch, piping generator function resulted in a cryptic error. We had to insert "|stringify" in this case. $ hg log --template '{if(author, author)|user}\n' abort: template filter 'userfilter' is not compatible with keyword '[(<function runsymbol at 0x7f5af2e8d8c0>, 'author'), (<function runsymbol at 0x7f5af2e8d8c0>, 'author')]'

--- a/tests/test-command-template.t	Wed Mar 11 15:22:34 2015 -0700
+++ b/tests/test-command-template.t	Tue Feb 24 00:04:55 2015 +0900
@@ -1901,6 +1901,11 @@
   hg: parse error: unknown function 'foo'
   [255]
 
+Pass generator object created by template function to filter
+
+  $ hg log -l 1 --template '{if(author, author)|user}\n'
+  test
+
 Test diff function:
 
   $ hg diff -c 8