Add fast --HEAD option to upstream-diff.

man/src/git-upstream-diff.txt

Index: man/src/git-upstream-diff.txt
diff --git a/man/src/git-upstream-diff.txt b/man/src/git-upstream-diff.txt
index e2aab356556507dbe8f29a55b9c8d9e83ff98697..aad48a4615d77274744e5a281fa488b794c419d4 100644
--- a/man/src/git-upstream-diff.txt
+++ b/man/src/git-upstream-diff.txt
@@ -41,6 +41,11 @@ OPTIONS
 --wordwise::
   Print a colorized word-wise diff instead of a line-wise diff.
 
+--HEAD::

[agable, 2014/05/07 00:57:48]

Not sure how I feel about the flag being capitalized. Does argparse enforce case
sensitivity for long-form flags? HEAD makes sense from a git perspective, but
capitalized long-form flags are really rare.

[iannucci, 2014/05/07 01:02:23]

Hm, but I don't think `--head` would make sense either.... What do you suggest?

+  Diff against the committed HEAD of your branch instead of your working copy.
+  This is 'substantially' faster on large repos, but doesn't take into account
+  uncommitted changes.

[szager1, 2014/05/07 06:48:32]

unstaged and uncommitted

+
 <extra args for git-diff>::
   Extra arguments are included in the invocation of linkgit:git-diff[1]. These
   can be anything that `git-diff` normally takes.