#397 Enable versioning and roll-back

[Erik Hänel]

Enable versioning and rollback by the use of the *.backup files created during saving a file.

Analysis:

Because the typical file size is somewhere around a few ten kilo bytes, a simple compression algorithm like ZIP will save enough space (around a fourth). Therefore, the following approach appears to be reasonable:

• Create hidden .revisions folders in the file root directories (like <loadpath>) and exclude them from the file traversers used to create the file tree
• During saving, create the backup file as an ZIP archive in the hidden root directories according <CURRENTPATH>/.revisions/FOLDER/STRUCTURE/FILENAME.EXT.revisions
• Add the contents of the current file to the archive as revXYZ
• Write the number of revisions into the ZIP comment section
• Add a possibility to visualize the number of revisions in the file tree
• Add a possibility to view the contents of a revision in the editor
• Add a possibility to recreate the contents of a revision
• Re-use the backup setting to control the creation of revisions

Implementation:

• Implementation: The implementation was done as proposed by the analysis.
• Revision: [r612]
• Implementation test: Multiple files were modified and the revision history was examined. No deviations detected

Documentation:

• [x] ChangesLog updated
• [x] Code changes commented
• Documentation articles:
  • [ ] corresponding documentation articles updated
  • [x] new documentation articles created
  • [ ] not needed
• Language files:
  • [x] corresponding language files updated
  • [ ] not needed

Tests:

Functionality was tested in productive environment. All deviations were resolved.