* io.c (rb_f_open): add rdoc about specifying ext_enc as *-bom.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@24213 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Mon Jul 20 20:35:55 2009  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* io.c (rb_f_open): add rdoc about specifying ext_enc as *-bom.
+
 Mon Jul 20 19:00:58 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* compile.c (compile_dstr_fragments): reduced needless literal.

io.c

@@ -5467,6 +5467,9 @@ check_pipe_command(VALUE filename_or_command)
  *  read string will be tagged by the encoding in reading,
  *  and output string will be converted
  *  to the specified encoding in writing.
+ *  If ext_enc ends with '-bom', check whether the input has a BOM. If
+ *  there is a BOM, strip it and set external encoding as
+ *  what the BOM tells. If there is no BOM, use ext_enc without '-bom'.
  *  If two encoding names,
  *  ext_enc and int_enc (external encoding and internal encoding),
  *  are specified, the read string is converted from ext_enc