templater: apply "stringify()" on sub expression to get string correctly

Templating syntax allows nested expression to be specified as parts
below, but they are evaluated as a generator and don't work correctly.

  - 'sep' of 'join(list, sep)'
  - 'text' and 'chars' of 'strip(text, chars)'

In the former case, 'sep' returns expected string only for the first
separation, and empty one for the second or later, because the
generator has only one element.

In the latter case, templating is aborted by exception, because the
generator doesn't have 'strip()' method (as 'text') and can't be
passed as the argument to 'str.strip()' (as 'chars').

This patch applies "stringify()" on these sub expression to get string
correctly.

mercurial/templater.py

@@ -296,7 +296,7 b' def join(context, mapping, args):'
 
     joiner = " "
     if len(args) > 1:
-        joiner = args[1][0](context, mapping, args[1][1])
+        joiner = stringify(args[1][0](context, mapping, args[1][1]))
 
     first = True
     for x in joinset:
@@ -328,9 +328,9 b' def strip(context, mapping, args):'
     if not (1 <= len(args) <= 2):
         raise error.ParseError(_("strip expects one or two arguments"))
 
-    text = args[0][0](context, mapping, args[0][1])
+    text = stringify(args[0][0](context, mapping, args[0][1]))
     if len(args) == 2:
-        chars = args[1][0](context, mapping, args[1][1])
+        chars = stringify(args[1][0](context, mapping, args[1][1]))
         return text.strip(chars)
     return text.strip()
 

tests/test-command-template.t

@@ -1659,3 +1659,12 b' Test branches inside if statement:'
 
   $ hg log -r 0 --template '{if(branches, "yes", "no")}\n'
   no
+
+  $ cd ..
+
+Test stringify on sub expressions
+
+  $ hg log -R a -r 8 --template '{join(files, if("1", if("1", ", ")))}\n'
+  fourth, second, third
+  $ hg log -R a -r 8 --template '{strip(if("1", if("1", "-abc-")), if("1", if("1", "-")))}\n'
+  abc