django-vff

Introduction

This package offers a file field for django models, that stores the file contents under a VCS (version control system). Everytime a field of this type is changed for a particular model instance, the new content will be commited as a new version in the repository. Thus, there will be one file in the repository for each vff field and instance. The repository will be at settings.VFF_REPO_ROOT, or, if that is unset, at a vf_repo subdirectory of django's settings.MEDIA_ROOT.

Different VCSs can be used to manage the repository, using pluggable backends. The package only provides a GIT backend out of the box.

Installation

Install django-vff like you would install any other pypi package:

$ pip install django-vff

You do not need to add anything into Django's INSTALLED_APPS.

Configuration

You have to set the following variables in django's settings.py:

VFF_BACKEND: A dotted name leading to a backend class, e.g. "vff.git_backend.GitBackend". This setting is required.

For the git backend:

VFF_REPO_ROOT: Absolute path to the location of the git repository. This repository may or may not exist before setting up django-vff.
VFF_REPO_PATH: Relative path within the git repository to the directory where django-vff keeps its managed files.

If these two settings for the git backend are not set, VFF_REPO_ROOT will assume a value of os.path.join(settings.MEDIA_ROOT, 'vf_repo'), and VFF_REPO_PATH will assume a value of ''.

Usage

You use it like you would use django.db.models.FileField:

from django.db import models
from vff.field import VersionedFileField


class MyModel(models.Model):
    name = models.CharField('Name', max_length=128)
    content = VersionedFileField(name='content', verbose_name='file content')

Once you have an instance of the MyModel class, you can use three special methods to list available versions, to get specific versions, and to get diffs between versions:

list revisions:

>>> revs = instance.content.list_revisions()
>>> from pprint import pprint
>>> pprint(revs)
[{'author': u'John Smith',
  'date': datetime.datetime(2011, 6, 16, 13, 25, 30),
  'message': u'second version',
  'versionid': 'a64ea785e195bbf4b3064e6701adbdbf4b5d13be'},
 {'author': u'Martha Brown',
  'date': datetime.datetime(2011, 6, 16, 8, 24, 36),
  'message': u'first version',
  'versionid': '048848a70205d0e18d836f403e2a02830492cbf9'}]

get the string content of a specific revision:

>>> rev1_id = revs[-1]['versionid']
>>> instance.content.get_revision(rev1_id)
u'These are the contents of the first version of the file'

get the diff between two revisions:

>>> rev2_id = revs[-2]['versionid']
>>> print instance.content.get_diff(rev1_id, rev2_id)
--- 048848a70205d0e18d836f403e2a02830492cbf9

+++ a64ea785e195bbf4b3064e6701adbdbf4b5d13be

@@ -1,1 +1,1 @@

-These are the contents of the first version of the file
+These are the contents of the second version of the file

Saving and deleting

At the moment, saving and deleting has to be explicitly done for this field. So, for example, if you have a model instance with a content vff field, and a view that uses an edit form with a forms.FileField for it, after validating the form you would have to do something like:

name = instance.content.name
content = form['content'].data
username = request.user.username
commit_msg = form['commit_msg'].data.encode('utf8')
instance.content.save(name, content, username, commit_msg)
instance.save()

Likewise, when removing an instance, you would:

username = request.user.username
commit_msg = u'entity removed'
instance.content.delete(username, commit_msg)
instance.delete()

In the future, if there is interest, the package could include a special widget with input space for the necessary data (commit message, etc) so that saving and deleting would be transparent.

Providing new backends

To develop a new backend for django-vff, you have to subclass the abstract base class vff.abcs.VFFBackend. The methods that need to be implemented are documented in the docstrings of the class.