Make gclient sync --force also ignore left over files when...

Make gclient sync --force also ignore left over files when
switching repositories.  This could result in clobbering
changes you may have in a third_party checkout, but if
you pass --force, I think you're asking for this behavior.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=48902

[tony, 2010-06-04 01:57:58]

This will allow the webkit.org bots to update when we roll in Chromium to
include scherkus' recent ffmpeg change.  Since the repo is moving, we want to
clobber it even if it has .vcproj or .mk or .xproject files.

I also look forward to the day when gyp generates project files outside the
tree.

[M-A Ruel, 2010-06-04 02:01:11]

lgtm