Add new flags to skdiff

Add new flags to skdiff

New flags are:
--nodiffs: don't write out image diffs or index.html, just generate report on stdout
--match: compare files whose filenames contain this substring; if unspecified, compare ALL files
         this flag may be repeated to add more matching substrings
--nomatch: regardless of --match, DO NOT compare files whose filenames contain this substring
           this flag may be repeated to add more forbidden substrings

Also implemented the --threshold flag, which was already documented but not implemented.
Committed: https://code.google.com/p/skia/source/detail?r=3806

[epoger, 2012-04-27 15:54:59]

This CL replaces http://codereview.appspot.com/6118056/ ('skdiff: if outputDir
is not specified, don't write out diff files at all') , and adds more
functionality.

[epoger, 2012-05-01 02:18:27]

On 2012/04/27 15:54:59, epoger wrote:
> This CL replaces http://codereview.appspot.com/6118056/ ('skdiff: if outputDir
> is not specified, don't write out diff files at all') , and adds more
> functionality.

ping?

[TomH, 2012-05-01 13:02:18]

Sorry! LGTM.

https://codereview.appspot.com/6135045/diff/1/tools/skdiff_main.cpp
File tools/skdiff_main.cpp (right):

https://codereview.appspot.com/6135045/diff/1/tools/skdiff_main.cpp#newcode1130
tools/skdiff_main.cpp:1130: }
Oh how far we have fallen from the Unix ideal of silent success.

[epoger, 2012-05-01 13:05:58]

https://codereview.appspot.com/6135045/diff/1/tools/skdiff_main.cpp
File tools/skdiff_main.cpp (right):

https://codereview.appspot.com/6135045/diff/1/tools/skdiff_main.cpp#newcode1130
tools/skdiff_main.cpp:1130: }
On 2012/05/01 13:02:18, TomH wrote:
> Oh how far we have fallen from the Unix ideal of silent success.

What good is success if you can't crow about it a little bit?
-D. Trump