Implement git clone -v

The new -v option forces the progressbar, even in case the output
is not a terminal.  This can be useful if the caller is an IDE or
wrapper which wants to scrape the progressbar from stderr and show
its information in a different format.

Signed-off-by: Miklos Vajna <vmiklos@frugalware.org>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
diff --git a/Documentation/git-clone.txt b/Documentation/git-clone.txt
index 0e14e73..95f08b9 100644
--- a/Documentation/git-clone.txt
+++ b/Documentation/git-clone.txt
@@ -90,6 +90,11 @@
 	Operate quietly.  This flag is also passed to the `rsync'
 	command when given.
 
+--verbose::
+-v::
+	Display the progressbar, even in case the standard output is not
+	a terminal.
+
 --no-checkout::
 -n::
 	No checkout of HEAD is performed after the clone is complete.