DiffView: add bzr support

[3v1n0]

Add support to bazaar VCS

[CJTozer]

Awesome, thanks for this!

I don't use bazaar - can you provide some examples for the readme for the valid diff args that are supported for bazaar? Don't mind if it's here or in an update to the PR.

[3v1n0]

This is what you get on bzr diff --help

Purpose: Show differences in the working tree, between revisions or branches.
Usage:   bzr diff [FILE...]

Options:
  --stat                Show diff summary statistics
  --old=ARG             Branch/tree to compare from.
  -v, --verbose         Display more information.
  -F ARG, --format=ARG  Diff format to use.
  --stat-dir            Show diff summary statistics per directory
  -q, --quiet           Only display errors and warnings.
  -p ARG, --prefix=ARG  Set prefixes added to old and new filenames, as two
                        values separated by a colon. (eg "old/:new/").
  --context=ARG         How many lines of context to show.
  --using=ARG           Use this command to compare files.
  --usage               Show usage message and options.
  --new=ARG             Branch/tree to compare to.
  -r ARG, --revision=ARG
                        See "help revisionspec" for details.
  --diff-options=ARG    Pass these options to the external diff program.
  -c ARG, --change=ARG  Select changes introduced by the specified revision.
                        See also "help revisionspec".
  -h, --help            Show help message.

Description:
  If no arguments are given, all changes for the current tree are listed.
  If files are given, only the changes in those files are listed.
  Remote and multiple branches can be compared by using the --old and
  --new options. If not provided, the default for both is derived from
  the first argument, if any, or the current tree if no arguments are
  given.

  "bzr diff -p1" is equivalent to "bzr diff --prefix old/:new/", and
  produces patches suitable for "patch -p1".

  Note that when using the -r argument with a range of revisions, the
  differences are computed between the two specified revisions.  That
  is, the command does not show the changes introduced by the first 
  revision in the range.  This differs from the interpretation of 
  revision ranges used by "bzr log" which includes the first revision
  in the range.

Exit values:
    1 - changed
    2 - unrepresentable changes
    3 - error
    0 - no change

Examples:
    Shows the difference in the working tree versus the last commit:

        bzr diff

    Difference between the working tree and revision 1:

        bzr diff -r1

    Difference between revision 3 and revision 1:

        bzr diff -r1..3

    Difference between revision 3 and revision 1 for branch xxx:

        bzr diff -r1..3 xxx

    The changes introduced by revision 2 (equivalent to -r1..2):

        bzr diff -c2

    To see the changes introduced by revision X:

        bzr diff -cX

    Note that in the case of a merge, the -c option shows the changes
    compared to the left hand parent. To see the changes against
    another parent, use:

        bzr diff -r<chosen_parent>..X

    The changes between the current revision and the previous revision
    (equivalent to -c-1 and -r-2..-1)

        bzr diff -r-2..

    Show just the differences for file NEWS:

        bzr diff NEWS

    Show the differences in working tree xxx for file NEWS:

        bzr diff xxx/NEWS

    Show the differences from branch xxx to this working tree:

        bzr diff --old xxx

    Show the differences between two branches for file NEWS:

        bzr diff --old xxx --new yyy NEWS

    Same as 'bzr diff' but prefix paths with old/ and new/:

        bzr diff --prefix old/:new/

    Show the differences using a custom diff program with options:

        bzr diff --using /usr/bin/diff --diff-options -wu

Aliases:  di, dif
From:     plugin "diffstat"

It includes examples, basically you can diff between revisions and branches