crecord: add dictionary to default return value of filterpatch

When committing interactively without changes, the user would get a ValueError
exception. This patch adds a dictionary to the return value of filterpatch
when there are no files to change.

mercurial/crecord.py

@@ -451,7 +451,7 b' def filterpatch(ui, chunks, chunkselecto'
 
     # if there are no changed files
     if len(headers) == 0:
-        return []
+        return [], {}
     uiheaders = [uiheader(h) for h in headers]
     # let user choose headers/hunks/lines, and mark their applied flags
     # accordingly

tests/test-commit-interactive-curses.t

@@ -41,6 +41,10 b' Committing some changes'
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     a
   
+Check that commit -i works with no changes
+  $ hg commit -i
+  no changes to record
+
 Committing only one file
 
   $ echo "a" >> a