keyword: suppress keyword expansion while 'hg backout' for internal merge

Before this patch, 'hg backout' may cause unexpected conflict, if 'hg
backout'-ed changes are located near lines in which keywords are
embedded, because keywords are substituted with other strings in the
working directory.

This patch suppresses keyword expansion while 'hg backout' for
internal merge by adding 'backout' to 'restricted' command list like
'merge'.

hgext/keyword.py

@@ -103,7 +103,7 b" nokwcommands = ('add addremove annotate "
 # hg commands that trigger expansion only when writing to working dir,
 # not when reading filelog, and unexpand when reading from working dir
 restricted = ('merge kwexpand kwshrink record qrecord resolve transplant'
-              ' unshelve rebase graft')
+              ' unshelve rebase graft backout')
 
 # names of extensions using dorecord
 recordextensions = 'record'

tests/test-keyword.t

@@ -1258,4 +1258,17 b' Test restricted mode with graft'
    $Xinfo$
   +xxxx
 
+Test restricted mode with backout
+
+  $ hg backout -q 11
+  $ hg diff a
+  diff -r 01a68de1003a a
+  --- a/a	Thu Jan 01 00:00:00 1970 +0000
+  +++ b/a	* (glob)
+  @@ -3,4 +3,3 @@
+   do not process $Id:
+   xxx $
+   $Xinfo$
+  -xxxx
+
   $ cd ..