[bug] git diff --word-diff gives wrong result for utf-8 chinese

Result of "git diff"

-  为1
+  为2

or (if chinese can not be displayed correctly)

-  <E4><B8><BA>1
+  <E4><B8><BA>2

Actual result of "git diff --color-words"

<E4><B8>[-<BA>1-]{+<BA>2+}

Expected result of "git diff --color-words"

为[-1-]{+2+}

or (if chinese can not be displayed correctly)

<E4><B8><BA>[-1-]{+2+}

Ping Yin