git-p4: handle utf16 filetype properly

One of the filetypes that p4 supports is utf16.  Its behavior is
odd in this case.  The data delivered through "p4 -G print" is
not encoded in utf16, although "p4 print -o" will produce the
proper utf16-encoded file.

When dealing with this filetype, discard the data from -G, and
instead read the contents directly.

An alternate approach would be to try to encode the data in
python.  That worked for true utf16 files, but for other files
marked as utf16, p4 delivers mangled text in no recognizable encoding.

Add a test case to check utf16 handling, and +k and +ko handling.

Reported-by: Chris Li <git@chrisli.org>
Acked-by: Luke Diamand <luke@diamand.org>
Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/fast-import/git-p4

@@ -1238,6 +1238,15 @@ class P4Sync(Command, P4UserMap):
             data = ''.join(contents)
             contents = [data[:-1]]
 
+        if file['type'].startswith("utf16"):
+            # p4 delivers different text in the python output to -G
+            # than it does when using "print -o", or normal p4 client
+            # operations.  utf16 is converted to ascii or utf8, perhaps.
+            # But ascii text saved as -t utf16 is completely mangled.
+            # Invoke print -o to get the real contents.
+            text = p4_read_pipe('print -q -o - "%s"' % file['depotFile'])
+            contents = [ text ]
+
         if self.isWindows and file["type"].endswith("text"):
             mangled = []
             for data in contents:
@@ -1245,6 +1254,8 @@ class P4Sync(Command, P4UserMap):
                 mangled.append(data)
             contents = mangled
 
+        # Note that we do not try to de-mangle keywords on utf16 files,
+        # even though in theory somebody may want that.
         if file['type'] in ('text+ko', 'unicode+ko', 'binary+ko'):
             contents = map(lambda text: re.sub(r'(?i)\$(Id|Header):[^$]*\$',r'$\1$', text), contents)
         elif file['type'] in ('text+k', 'ktext', 'kxtext', 'unicode+k', 'binary+k'):