This file documents the 'svnpatch' format that's used with both diff and patch
subcommands.

I HISTORY
  -------

[remind the reasons behind the design of such a new format]


II DIFF SUBCOMMAND FORMATS
   -----------------------

'svn diff' subcommand is provided with 3 formats:
  * default: useful for code reviewing
  * unidiff: fits better towards patch(1) use
  * svnpatch: supports any change


III SVNPATCH FORMAT
    ---------------

First off, let's define it.  svnpatch format is made of two ordered parts:
  * (a) human-readable: made of unidiff bytes
  * (b) computer-readable: made of svn protocol bytes, gzip'ed, base64-encoded

But, as we're not in a client/server configuration:
  - (b) only uses svn protocol's Editor Command Set, there's no need for the
    Main Command Set nor the Report Command Set
  - a client reads Editor Commands from the patch, i.e. the patch silently
    drives the client's editor
  - the only direction the information takes is from the patch to the client
  - svndiff1 is solely used instead of being able to choose between svndiff1
    and svndiff0

Such a format can be seen as a subset of svn protocol which:
  - Capabilities and Edit Pipelining have nothing to do with as we can't adjust
    once the patch is rock-hard written in the file nor negotiate anything
  - commands are restricted to the Editor Command Set

For more about Command Sets, consult libsvn_ra_svn/protocol.


IV FORMATS DIFFERENCES
   -------------------

In similar use-cases, svnpatch's (a) may vary from the two other formats
although they all three use unidiff.  For instance, a file add is represented
as a difference from /dev/null for the 'default' and 'unidiff' formats, while
it's stored within (b) when using 'svnpatch' hence missing from (a).  There are
more, the following table compares what each format outputs against each
operation:

               | default |  unidiff  |   svnpatch
  -------------+---------+-----------+-------------------------------------
  file add     |   +++   |    +++    | add-file
  file del     |   ---   |    ---    | delete-entry
  file move    |   ---   | +++ & --- | add-file w/ copy-path + delete-entry
  file copy    |         |    +++    | add-file w/ copy-path
               |         |           | 
  dir add      |         |           | add-dir
  dir del      |         |           | delete-entry
  dir move     |         |           | delete-entry + add-dir w/ copy-path
  dir copy     |         |           | add-dir w/ copy-path
               |         |           | 
  file propset |   +++   |           | change-file-prop
  dir propset  |   ---   |           | change-dir-prop

+++: unidiff '+' lines
---: unidiff '-' lines

To keep things clear, the svnpatch column is free from opening and closing
commands as well as a few others even though svnpatch uses the whole set of
Editor Commands.


X PATCHING
  --------

X FUZZING a.k.a. DYSTOPIA
  --------