Add option to ignore files from diff view but not VCS

Feature Request:

Background:

When working on projects that use an IDE for build configuration, it is often beneficial to include project files (such as Keil's .uvopt and .uvproj xml files) in the version control system. These are the files that contain the information necessary to build the project correctly - which files are included, compiler flags etc. However, they also contain information on which files were open last time the IDE was running and which variables were being watched in the debugger etc. As a result, it is common for them to change with virtually every commit.

As a result, when a diff or qdiff is done, it is quite common for there to be three screens of changes to the .uvopt xml file and three lines of changes to the source code. In almost all cases, I'm interested in the changes to the source code and not to the project files.

In other environments, some companies enforce a policy of including hex files or other generated files in the VCS - again, these would be unlikely to be of interest in a diff.

Proposal:

Add a new ignore file in a similar format to the existing ignore file, called something like ".bzrmeta/diff_ignore". This will have no effect on the normal commit, push, pull etc commands, but will be checked by bzr diff and bzr qdiff and the files that match will be omitted from the diff report, just as if they were binary files. An additional command-line option could be added (e.g. --all-files) to explicitly override the diff ignore list.