Fix output of rbt diff/post for git when -X specified.

Review Request #6350 — Created Sept. 21, 2014 and submitted — Latest diff uploaded

Information

RBTools
release-0.6.x
3492099...

Reviewers

Currently, git's filter support does the opposite behaviour
(only includes files that match all exclude_patterns).

A new module, rbtools.utils.diffs, specifies helper functions
filename_match_any_patterns, which determines if a filename matches
at least one of the given patterns, and
remove_filenames_matching_patterns, which returns an iterable of the
filenames that do not match any given pattern.

The parameters to git diff and git diff-tree have been
reordered so that the revision specification is always the last
argument before the filenames.

All unit tests pass now.
Generated diffs with rbt diff in a git repository with more than
one file changed. When -X filename was specified, only that
file's diff was excluded from the output.