Subversion Offline Solution (SOS)

## List of Abbreviations and Definitions

• PyPI: Python Package Index

• SCM: Source Control Management

• SOS: Subversion Offline Solution (this tool)

• VCS: Version Control System

• Filename: Fixed term for file names used throughout SOS and this documentation

• File pattern: A filename or glob, allowing to place special characters like *?[!] into file names to mark ellipses

• File tree: A directory structure on the user’s file system at a certain point. It’s not exactly the same as a checkout or working copy, but largely comparable

• Revision: An archived (or versioned, differential) set of file modifications, also known as changeset or patch

### Introduction

If you (love, or simply have to) work with the SVN VCS, but need (or lack) the flexibility of committing and branching files offline (without a permanent network connection) similar to how Git is able to, SOS is your straight-forward and super simple command-line SCM solution.

SOS allows performing offline operations a) as a drop-in replacement for svn and other VCS, b) as an offline extension of those VCSs that either don’t support offline branching and committing or are too complex, and c) as a standalone VCS. You may run sos offline not only inside a SVN checkout, but in any (and also multiple, even nested) folders of your file system, even outside of VCS repository checkouts/clones.

SOS thus augments SVN with offline operation and serves the same need as SVK, RCS, CVS, Git, gitless, monotone, darcs, Bazaar, Mercurial, and Fossil.

As an additional practical benefit, the sos command will double as the command line interface of any popular VCS and will execute any svn, git, etc. command by sos <command> [<arguments-and-options>], e.g. sos commit -m "Message" instead of svn commit -m "Message" or git commit -m "Message". Once you executed sos offline, however, all commands are interpreted by the SOS tool instead, until leaving the offline mode via sos online (with the exception of sos config, cf. details below).

## Flexible VCS Modes

SOS supports three different file handling models that you may use to your liking, thus being able to mimick different traditional VCSs, plus a new mode for super quick and easy version management (the default). - Simple mode: All files are automatically versioned and tracked. Drawback: Will pickup any little modification for any file, binary or not, unless put on an ignore list - Tracking mode: Only files that match certain file patterns are respected during commit, update and branch (just like in SVN, gitless, and Fossil), requiring users to specifically add or remove files per branch. Drawback: Need to declare files to track for every offline repository - Picky mode: Each operation needs the explicit declaration of file patterns for versioning (like Git does). Drawback: Need to stage files for every single commit

## Unique Features of SOS

• Initializes repositories by default with the simple mode, which makes effortless versioning a piece of cake

• In the optional tracking mode, files are tracked via file patterns instead of pure filenames or paths (in a manner comparable to how SVN ignores files)

• Command line replacement for traditional VCS that transparently pipes commands to them

• Straightforward and simplified semantics for common VCS operations (branch, commit, integrate changes)

## Limitations

• Designed for use by single user, network synchronization is a non-goal. Don’t attempt to use SOS in a shared location, concurrent access to the repository may corrupt your data, as there is currently no locking in place for atomic operations (could be augmented to avoid concurrent access from two terminals, though)

• Has a small user base as of now, therefore no reliable reports of compatibility and operational capability except for the automatic unit tests run on Travis CI and AppVeyor

## Compatibility

• SOS runs on any Python 3.4 distribution or higher, including some versions of PyPy. Python 2 is not supported anymore due to library issues, although SOS’s programming language Coconut is generally able to transpile to valid Python 2 source code. Use pip install sos-vcs[backport] to attempt running SOS on Python 3.3 or earlier

• SOS is compatible with above mentioned traditional VCSs: SVN, Git, gitless, Bazaar, Mercurial and Fossil

• Filename encoding and console encoding: Full roundtrip support (on Windows) started only with Python 3.6.4 and has not been tested nor confirmed yet for SOS

## Documents

• See the tutorial to make your first steps with SOS.

• See the integration guide for information on integrating SOS into your Desktop environment.

• See the contribution guideline for further information on how to help with developing SOS.

### Latest Changes

• Version 1.7, soon to be released: Hint: The fast branching features is usable but still seen as experimental.

• Feature 265 Experimental support for remote (secondary, backup, storage) repository locations. This feature allows replicating all operations (i.e. commits) into (passive, read-only) secondary repository locations. To enable this feature, either go offline with one or more additional --remote <file system path> arguments, or manually put a copy of your repository metadata folder (.sos) somewhere else, set the metadata flag "remote": true inside its .sos/.meta and put the just created remote copy’s parent folder into the remotes list inside the .sos/.meta file of your primary repository. To restore a remote backup, make a copy of it and set the remote flag in .sos/.meta to false

• Feature 265, 269, 289, 290 Added remote copies feature; remote copies are marked as read-only to avoid accidental conflicts. All write operations will also perform actions on all remote repository copies. To limit the affected remotes in a command, use either --no-remotes or --exclude-remote[s] and --include-remote[s] with paths that match configured remote paths

• Feature 256 Added colorful console output for diff, changes, config, status and log comands

• Feature 238, 262, 264 Optional relative path output

• Enhancement 285 Allow both --exclude for --except and --include for --only

• Enhancement 284 Allow --only=argument syntax for --only argument

• Enhancement 249 Internal performance refactoring

• Enhancement 239 Showing progress bar during log traversal

• Enhancement 234 Better move detection heuristic in case of multiple equal files

• Enhancement 225 Adding overall commit size in status messages

• Enhancement 193 Adding processed file numbers in status messages

• Bug 283 Avoid empty files shown as modified

• Version 1.6, released on 2018-05-14:

• Feature 77 Feature to commit branches to underlying VCS

• Feature 127, 218 Implement much better help system

• Feature 209 Added warning when committing a file with a older timestamp than its previous revision or previous commit

• Feature 210 Logic coding bug that prevented the distinction between full or differential dump to work

• Feature 212 Limit number of displayed revisions in sos log. Can be controlled by option flag --all and configuration setting logLines

• Feature 213 Now displaying occupied storage space

• Enhancement 144 Make a semantic distinction between verbose output using --verbose and debugging output using --debug and --log

• Enhancement 173 Changed the way how merge options are handled - now allowing to remember one decision for the remainder of a file

• Enhancement 201, 208 Added a project logo

• Enhancement 211 Add a fancy ASCII art title

• Enhancement 214 More documentation

• Enhancement 216 Change display in sos log to display number of modified text files instead of added text files

• Enhancement 222, 218 Better sos help display and sorting

• Enhancement 227 Sligthly modified diff output format

• Bug 217 Wrong path displayed in sos status

• Bug 219 Error in revision computation leading to switching not working correctly between fast-branched branches

• Bug 221 Display of wrong number of files on sos commit

• Bug 230, 219 Fixed bugs in destroy that could lead to errors when removing empty branches

• QA 198 Finally made the tests run on AppVeyor. Reason was file system synchronization problems not shown on Linux

• Version 1.5, released on 2018-03-03:

• Bug 78 Long standing bug, computing wrong line numbers in diff view

• Bug 196 Ubiquitous --only and --except options not working

• Bug 197 Bug fix for shown number of files in commit and log

• Bug 206, 207 Merge not asking for user input on one-line replace, also wrong use of mine/theirs

• Enhancement 195 Minimize the number of digits in diff line numbers to the required amount

• Enhancement 199 Unicode symbols added (force set via useUnicodeFont)

• Enhancement 202 Now using the wcwidth library to determine visible width of unicode strings (untested)

• Feature 102 Option to list tracking patterns, and list (tracked) files recursively

• Feature 157, 200, 204 Experimental support for incremental dumps

• Version 1.4, released on 2018-02-17:

• Bug 167 Accidentally crawling file tree and all revisions on sos status

• Bug 190 Changes not computed in sos online

• Enhancement 75 Better progress indicators during sos commit and other operations

• Enhancement 133 Now showing entire repository compression advantage after sos offline and sos commit

• Enhancement 171 Display target end-of-line type in sos diff

• Enhancement 179, 180 SOS now creates backups from metadata files and dump files automatically

• Enhancement 186 Option to ignore leading and trailing white space in sos diff (not useful for sos update, though)

• Enhancement 187 By default, text in sos diff is cut at the end of the (right-hand) terminal border, with the option switch --wrap to retain the old behaviour (wrapping text around)

• Enhancement 191 Allow to make the behavior of the sos status command configurable via useChangesCommand=yes to either show file tree status (the new default, mirroring the behaviour of SVN and Git), or display the repository and branches status (while having sos changes for file tree status instead, especially for people coming from Fossil)

• Enhancement 192 Reduced lines of code by relying on latest enhancements in Coconut (e.g. typing imports), plus removing obsolete code

• Feature 181 Introduces experimental code for very fast branching. Use sos branch [<name> [<message>]] --last --fast for instant branching that uses only a reference to the parent branch instead of copying each file. This feature goes a step into the direction of Git and introduces complexity into the code base, but was seen as essential to not stand in the way of the developer. The burden of copying revisions to dependant branches is delayed to when the parent branch is destroyed, assuming that destroying a branch is an action much less often used than branching

• Feature 182 Introduces automatic upgrade for metadata format, making manual migration steps of previous and any future releases obsolete

• Feature 183 SOS now recognizes and displays renames and file moves inside the repository. The underlying add/remove file behaviour is unchanged, but the user sees a moved notification for sos changes and sos commit

• Version 1.3, released on 2018-02-10:

• Enhancement 152, 162 PEP528/529 compatibility: Now working with any console encoding and file system encoding on Windows (at least with Python 3.6+)

• Enhancement 163 Rewrite of changeset handling to avoid problems when re-adding files deleted in previous revision

• Enhancement 164 Little improvement for sos config

• Enhancement 165 Little improvement for sos config add

• Enhancement 168 Don’t stop switching if changes are same as live modifications

• Feature 64 Added blacklisting for tracking patterns (e.g. to except single files or reduce scope of globs). For manual migration from older repositories: Add a , [] at the end of each branch info inside .sos/.meta, e.g. modify

[0, 1518275599353, "trunk", true, []]

to

[0, 1518275599353, "trunk", true, [], []] (note the additional trailing , [])

• Version 1.2, released on 2018-02-04:

• Version 1.1, released on 2017-12-30:

• Bug 90 Removed directories weren’t picked up

• Bug 93 Picky mode lists any file as added

• Enhancement 63 Show more change details in log and status, and also ls (in #101)

• Enhancement 86 Renamed command for branch removal to destroy

• Feature 8 Added functionality to rename tracking patterns and move files accordingly

• Feature 61 Added option to only consider or exclude certain file patterns for relevant operations using --only and --except. Note: These have to be already tracked file patterns, currently, see #99 and #100

• Feature 80 Added functionality to use tags

• QA 79 Added AppVeyor automated testing

• QA 94 More test coverage

• Many little fixes and improvements

• Version 1.0, released on 2017-12-14:

• First release with basic functionality

• Lots of test cases, good test coverage

• System integration and packaging

• Library integration and testing

• VCS integration

### Comparison with Traditional VCSs

While completing version 1.0 of SOS after almost two months of development, I incidentally discovered an interesting article by Gregory Szorc that discusses central weaknesses in the design of popular VCSs, with a focus on Git. Many of his arguments I have intuitively felt to be true as well and were the reason for the development of SOS: mainly the reduction of barriers between the developer’s typical workflow and the VCS, which is most often used as a structured tool for “type and save in increments”, while advanced features of Git are just very difficult to remember and get done right.

• While Git is basically a large key-value store with a thin access interface on top, SOS keeps a very clear (folder) structure of branches, revisions and files

• Compared to SVN, SOS’s file store is much simpler and doesn’t require an integrated database, and recovery is manually possible with little effort

Here is a comparison between SOS and traditional VCS’s commands: - branch creates a branch from the current file tree, but also switches to it immediately. There is no requirement to name branches, removing all barriers - SOS allows to branch from the latest committed revision via sos branch [<name>] --last; this automatically applies when in tracking and picky mode. In consequence any changes performed since last commit will automatically be considered as a change for the next commit on the branch unless --stay was added as well, to not switch to the new branch - Using the --fast option will store a reference to the originating branch and revision instead of copying all files. This option is currently only available when also using --last to avoid confusion on what data is considered (not the current file tree, but the last committed revision) - All tracking patterns will be copied to the new branch and can be modified there independently - commit creates a numbered revision from the current file tree, similar to how SVN does, but revision numbers are only unique per branch, as they aren’t stored in a global namespace. The commit message is strictly optional on purpose (as sos commit serves largely as a CTRL+S replacement) - The first revision (created during execution of sos offline or sos branch) always has the number 0 - Each sos commit increments the revision number by one; revisions are referenced by this numeric index, the revision’s optional commit message if given, or a tag - Tagging a commit means that the commit message serves as a tag name and is assured to be unique. Referring to a revision by its tag name can be used instead of numeric revision index, but works not only for tagged revisions and finds the first matching revision with a matching commit message - You may use negative revision indexes, just like Python does. -1 refers to the latest revision, -2 to the second-latest - You may specify a revision of the current branch by /<revision>, while specifying the latest revision of another branch by <branch>/ (note the position of the slash) - delete destroys and removes a branch. It’s a command, not an option flag as in git branch -d <name> for usability’s sake - add and rm add and remove tracking patterns, if the repository was created in tracking or picky mode. Patterns are never recursively applied, but always apply for a specific file tree path. They may contain, however, globs in their filename part, which makes it different from any other VCS in existence - move renames a file tracking pattern and all matching files accordingly; only useful in tracking or picky mode. It supports reordering of literal substrings, but no reordering of glob markers (*, ? etc.), and of adjacent glob markers. Use --soft to avoid files actually being renamed in the file tree. Warning: the --force option flag will be considered for several consecutive, potentially dangerous operations - switch works like checkout in Git for a revision of another branch (or of the current), or update to latest or a specific revision in SVN. Please note that switching to a different revision will in no way fix or remember that revision. The file tree will always be compared to the branch’s latest commit for change detection - update works a bit like pull and merge in Git or update in SVN and replays the specified other (or “remote”’s) branch’s and/or revision’s changes into the file tree. There are plenty of options to configure what changes are actually integrated, plus interactive integration. This command will not switch the current branch like switch does. Note, that this is not a real 3-way merge, or merge at all, just a more flexible way to insert and remove text output from diff.

When differing contents are to be merged, there is always a potential for conflict; not all changes can be merged automatically with confidence. SOS takes a simplistic and pragmatic approach and largely follows a simple diff algorithm to detect and highlight changes. Insertions and deletions are noted, and modifications are partially detected and marked as such. There are different layers of changes that SOS is able to work on:
- File addition or removal in the file tree, e.g. when updating from another branch and/or revision or switching to them, can be controlled by --add, --rm and --ask, which applies only for conflicts. Default is to replay both
- Line insertion or deletion inside a file, e.g. when merging file modifications during update, via --add-lines, --rm-lines, --ask-lines. Default is replay both
- Character insertion or deletion on a single text line being mergedf, e.g. when non-conflicting intra-line differences are detected, via --add-chars, --rm-chars, --ask-chars. Default is to replay both
- Updating state from another branch in the --track or --picky mode will always combine (build the union of) all tracked file patterns. To revert this, use the switch --meta command to pull back in another branch's and/or revision's tracking patterns to the currently active branch (may require to switch first to the other side). There is currently no check, if the pulled in tracking patterns are supersets or subsets of the onces being already there
- There may be, however, blocks of text lines that seem inserted/deleted but may have actually just been moved inside the file. TODO: SOS attempts to detect clear cases of moved blocks and silently accepts them no matter what. TODO: implement and introduce option flag to avoid this behavior

## Working in Track and Picky Modes

Use the commands sos add <pattern> or sos rm <pattern> to add or remove file patterns. These patterns always refer to a specific (relative) file paths and may contain globbing characters ?*[!] only in the filename part of the path.

### Configuration Options

These options can be set or unset by the user and apply either globally for all offline operations the user performs from that moment on, or locally to one repository only (using the --local option flag). There is currently no --system scope (like Git supports), because SOS has been designed mainly as a single-user tool and we don’t want to patronize users. Some of these options can be defined on a per-repository basis already during offline repository creation (e.g. sos offline --track --strict --compress), others can only be set in a persistant fashion (e.g. sos config set texttype "*.xsd"), or after repository creation (e.g. sos config set texttype "*.xsd;*.xml" --local).

## Configuration Commands

• sos config set sets a boolean flag, a string, or an initial list (semicolon-separated)

• sos config unset removes a boolean flag, a string, or an entire list

• sos config add adds one or more (semicolon-separated) string entry/entries to a list, and creates it if necessary

• sos config rm removes a string entry from a list. Must be typed exactly as the entry to remove. To remove the list, use sos unset <key>

• sos config show lists all defined configuration settings, including storage location/type (global, local, default)

• sos config show <parameter> show only one configuration item

• sos config show flags|texts|lists show supported configurations settings per type

## User Configuration and Defaults

SOS uses the configr <https://github.com/ArneBachmann/configr>__ library to manage per-user global defaults, e.g. for the --strict and --track flags that the offline command takes, but also for often-used file and folder exclusion patterns. By means of the sos config set <key> <value> command, you can set these flags with values like 1, no, on, false, enable or disabled.

## Available Configuration Settings

• strict: Flag for always performing full file comparsion, not only relying on modification timestamp; file size is checked always in both modes. Default: False

• track: Flag for defaulting to tracking mode when going offline (SVN-style). Default: False

• picky: Flag for defaulting to picky mode when going offline (Git-style). Default: False

• compress: Flag for compressing versioned artifacts using bzip2. Default: False

• useChangesCommand: Flag for making sos status into sos status --repo and using sos changes instead of sos status to more closely copy Fossil’s behaviour

• useColorOutput: Flag for coloring console output. Default: Depends on operating system and available libraries

• useUnicodeFont: Flag to use more fancy symbols, granted the console font supports them. Default: Depends on operating system

• defaultbranch: Name of the initial branch created when going offline. Default: Dynamic per type of VCS in current working directory (e.g. master for Git, trunk for SVN, no name for Fossil)

• texttype: List of file patterns that will be handled as text files, thus can be merged via textual diff, in addition to what Python’s mimetypes library will detect as a text/... mime. Example: *.bak could be a text file on your system, so add it to the texttype configuration, either globally (default) or locally (using --local). Default: Empty list

• bintype: List of file patterns that should be recognized as binary files which cannot be merged textually, overriding potential matches in texttype. Default: Empty list

• ignores: List of global file patterns (without any folder path) to ignore during repository operations. Any file match from the corresponding white list will negate any hit for ignores. Default: Check utility.coco in the source code; defaults contain e.g. ["*.bak", "*.py[cdo]]"

• ignoresWhitelist: List of file patterns to be consider even if matched by an entry in the ignores list. Default: Empty list

• ignoreDirs: As ignores, but matching folder names (not full paths)

• ignoreDirsWhitelist: As ignoresWhitelist, but for folder names

### Noteworthy Details

• SOS doesn’t store branching point information (or references); each branch stands alone and has no relation whatsoever to other branches or certain revisions thereof, except incidentally its initial file contents

• File tracking patterns are stored per branch, but are not versioned together with commits. This means that the “what to track” metadata is not part of the changesets. This is a simplification stemming from the main idea that revisions form a linear order of savepoints, and users rarely go back to older revisions

• sos update will not warn if local changes are present. This is a noteworthy exception to the failsafe approach taken for most other commands

• Detection of text types works solely on the file extension and user-defined patterns. In case the decoding of a text file fails, an error is shown

### Recipes

• Diff between any two revisions: Switch to the revision you want to compare against, then perform a diff with the other revision as argument

• Ignore whitespaces during diff: Add the option --iw or --ignore-whitespace

• Revert all changes except for certain files: Use sos switch / --except "glob*" --except ... or use sos switch / --only "glob*"

### Hints and Tipps

• To migrate an offline repository, either use the sos dump <targetname>.sos.zip command, or simple move the .sos folder into an (empty) target folder, and run sos switch trunk --force (or use whatever branch name you’re wanting to recreate). For compressed offline repositories, you may simply tar all files, otherwise you may want to create an compressed archive for transferring the .sos folder

• To save space when going offline, use the option sos offline --compress: It may increase commit times by a noticeable factor (e.g. 10x), but will also reduce the amount of storage needed to version files. To enable this option for all future offline repositories, use sos config set compress on

• When specifying file patterns including glob markers on the command line, make sure you quote them correctly. On Linux (bash, sh, zsh), but also often in Windows, put your patterns into quotes ("), otherwise the shell might replace file patterns by the list of any matching filenames instead of forwarding the pattern literally to SOS

• Many commands can be shortened to three, two or even one initial letters, e.g. sos st will run sos status, just like SVN does (but sadly not Git). Using SOS as a proxy to other VCS requires you to specify the form required by those, e.g. sos st works for SVN, but not for Git (use sos status instead)

• It might in some cases be a good idea to go offline one folder higher up in the file tree than your base working folder to care for potential deletions, moves, or renames

• The dirty flag is only relevant in tracking and picky modes TODO investigate - is this true, and if yes, why

• Branching larger amounts of binary files may be expensive as all files are copied and/or compressed just like during sos offline. A workaround is to sos offline only in the folders that are relevant for a specific task

• If you see the Windows system error [Errno 13] (hinting at a permission problems), don’t go looking for user right problems, rather check for other processes locking files in the file tree and try again

• For files detected as being moved or renamed, using --only or --except for just the old or new path will lead to either only removing the old file path or only adding the new entry, prohibiting it to be recognized as a move action in the history, since the other half of the move action is missing

### Ideas for future developments:

• Issue 158 Remote metadata folder would allow separating the repository from the checkout, and - in combination with a locking library like fasteners could even be used as a multi-user repository. Estimated development/testing effort is 3+3 hours.

### Release Management

• Increase version number by running python3 setup.py release

• Run python3 setup.py clean build test to update the PyPI version number, compile and test the code. If you need elevated rights to do so, use sudo -E python....

• Run git add, git commit and git push and let Travis CI and AppVeyor run the tests against different target platforms. If no problems appear, continue:

• Run python3 setup.py sdist

• Don’t forget to tag releases in the git history and on Github

• Run twine upload dist/*.tar.gz to upload the previously created distribution archive to PyPI.

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