bug#17945: 24.4.50; vc-git-annotate-command is too slow

[William Xu]

C-x v g on a git file is very slow, compare this:

    $ time git --no-pager  blame  -- vc-annotate.el 1>/dev/null

    real    0m1.432s
    user    0m1.364s
    sys    0m0.063s


    $ time git --no-pager  blame -C -C  -- vc-annotate.el 1>/dev/null

    real    0m23.477s
    user    0m22.058s
    sys    0m1.405s

It seems the -C -C options would slow down git hugely, making this
command almost useless.  Can we remove it from default option list?

-William

git version 1.9.3

In GNU Emacs 24.4.50.1 (i386-apple-darwin13.1.0, NS apple-appkit-1265.19)
 of 2014-04-16 on tokyolove.local
Windowing system distributor `Apple', version 10.3.1265
Configured using:
 `configure --with-ns CC=clang'

Configured features:
ACL GNUTLS LIBXML2 ZLIB

Important settings:
  locale-coding-system: utf-8-unix