Better SCM Initiative : Comparison

Version Control System Comparison

This is a comparison of version-control systems. It is split into several categories and sub-categories under which the systems are checked.

Timestamp: $Id: scm-comparison.xml,v 3f0f001880e7 2012/08/25 09:01:19 shlomif $

Repository Operations

Atomic Commits

Support for atomic commits means that if an operation on the repository is interrupted in the middle, the repository will not be left in an inconsistent state. Are the check-in operations atomic, or can interrupting an operation leave the repository in an intermediate state?

CVS No. CVS commits are not atomic.
AccuRev Yes. Commits are atomic
Aegis Commits are atomic.
AllChange Yes. Commits are atomic.
Arch Yes. Commits are atomic.
Bazaar Yes. Commits are atomic.
BitKeeper Yes (but need to verify)
ClearCase Yes. Commits (checkins) are atomic.
CM+ Yes. Commits are atomic.
CMSynergy Yes. Commits are atomic.
Co-Op Yes. Commits are atomic.
Darcs Yes. Commits are atomic.
Fortress Yes. Commits are atomic.
Fossil Yes. Commits are atomic.
Git Yes. Commits are atomic.
LibreSource Synchronizer Yes. Commits and updates are atomic.
Mercurial Yes.
Monotone Yes.
OpenCM Yes. Commits are atomic.
Perforce Yes. Commits are atomic.
PureCM Yes. Commits are atomic.
SourceAnywhere Yes. Commits are atomic.
Subversion Commits are atomic.
Superversion Commits are atomic.
Surround SCM Commits are atomic.
svk Commits are atomic.
Team Foundation Server Yes. Commits are atomic.
Vault Yes. Commits are atomic.
Vesta Yes. Commits are atomic.
Visual SourceSafe No. VSS commits are not atomic.

Files and Directories Moves or Renames

Does the system support moving a file or directory to a different location while still retaining the history of the file? Note: also see the next section about intelligent merging of renamed paths.

CVS No. Renames are not supported and a manual one may break history in two.
AccuRev Yes. Renames of both files and directories are supported. Supports controlling of symbolic links as well.
Aegis Yes. Renames are supported.
AllChange Yes. Renames are supported.
Arch Yes. Renames are supported.
Bazaar Yes. Renames are supported for files and directories.
BitKeeper Yes. Renames are supported.
ClearCase Yes. Directories are first-class controlled entities in Clearcase. Even supports controlling of symbolic/hard links.
CM+ Yes. Both moves and renames are supported, while maintaining history.
CMSynergy Yes. Renames are supported.
Co-Op Renames of files are supported. Renaming a directory requires creating a new one, moving the files and deleting the old one. Moved file histories are preserved.
Darcs Yes. Renames are supported.
Fortress Yes. Both moves and renames are supported, while maintaining history.
Fossil Moves and renames are supported. History is retained.
Git Renames are supported for most practical purposes. Git even detects renames when a file has been changed afterward the rename. However, due to a peculiar repository structure, renames are not recorded explicitly, and Git has to deduce them (which works well in practice).
LibreSource Synchronizer Yes. Renames and move are supported but the working copy needs to be up-to-date before doing a rename/move operation. This operation will be committed directly.
Mercurial Yes. Renames are supported.
Monotone Yes. Renames are supported.
OpenCM Yes. Renames are supported
Perforce Yes, supported since version 2011.1.
PureCM Yes. File and folder renames and moves are directly supported.
SourceAnywhere Yes. Both moves and renames are supported, while maintaining history.
Subversion Yes. Renames are supported.
Superversion No. Renames are not supported.
Surround SCM Renames are supported, moves can be accomplished similiar to SourceSafe.
svk Yes. Renames are supported.
Team Foundation Server Yes. Both moves and renames are supported, while maintaining history.
Vault Yes. Both moves and renames are supported, while maintaining history.
Vesta Yes. The unit of checkout/checkin is a directory tree. Files and directories can be added, deleted, and renamed between versions.
Visual SourceSafe Affects the whole history, it's like renaming a file in the CVS repository. There is a kludgy workaround using "share-rename,move,delete" that gets what you want.

Intelligent Merging after Moves or Renames

If the system keeps tracks of renames, does it support intelligent merging of the files in the history after the rename? (For example, changing a file in a renamed directory, and trying to merge it).

CVS No. Renames are not supported at all, much less intelligent ones.
AccuRev Unknown. FILL IN.
Aegis Unknown. FILL IN.
AllChange Partial. Move is implemented as copy+delete/obsolete, full revision history is maintained across copying, so changing a file in the copied directory does the right thing.
Arch Yes. Renames can be merged intelligently.
Bazaar Yes. Renames are intelligent.
BitKeeper Unknown. Probably Yes.
ClearCase Yes, renames and moves are intelligent in ClearCase and are handled well. Every unique file is given a UUID and directory entries map names to UUIDs, so moving a file around preserves its UUID. Doesn't work across VOBs.
CM+ Yes. Renames are Intelligent.
CMSynergy Unknown. FILL IN.
Co-Op Unknown. FILL IN.
Darcs Yes, renames are intelligent but should be explicitly specified using "darcs mv" because they are not detected automatically.
Fortress Yes, intelligent renames are supported.
Fossil Yes, intelligent renames are supported.
Git No. As detailed in the Git FAQ: "Git has a rename command git mv, but that is just a convenience. The effect is indistinguishable from removing the file and adding another with different name and the same content."
LibreSource Synchronizer Yes. Renames are intelligent. However, the rename should be made by the system, in order to be detected in the right manner.
Mercurial Yes, intelligent merging after renames is supported. the Mercurial book says: "If I modify a file, and you rename it to a new name, and then we merge our respective changes, my modifications to the file under its original name will be propagated into the file under its new name. (This is something you might expect to 'simply work,' but not all revision control systems actually do this.)"
Monotone Yes. Intelligent merging is fully supported.
OpenCM Unknown.
Perforce See point above.
PureCM Yes, intelligent renames are supported.
SourceAnywhere Unknown. FILL IN.
Subversion No. "svn help mv" says "Note: this subcommand is equivalent to a 'copy' and 'delete'." There's a bug report about it.
Superversion No. Renames are not supported.
Surround SCM Yes. Renames can be merged intelligently.
svk No. Same as Subversion.
Team Foundation Server Unknown. FILL IN.
Vault Yes, intelligent renames are supported.
Vesta Unknown. FILL IN.
Visual SourceSafe No, renames are not intelligent.

File and Directory Copies

Does the version control system support copying files or directories to a different location at the repository level, while retaining the history?

CVS No. Copies are not supported.
AccuRev Copying is supported through symbolic links (but all linked files are treated as the same file version). Moves are fully supported with the history retained.
Aegis No. Copies are not supported.
AllChange Yes. Copies are supported.
Arch No. Copies of files and directory structures are not supported.
Bazaar No. Copies are not supported.
BitKeeper Yes. Copies are supported.
ClearCase Yes, through use of hard links. (But some limitations in Windows environments)
CM+ Yes. An inexpensive operation that can be used for sharing files in multiple places. On deploy, you have the option of deploying only one of the shared files or all of them.
CMSynergy Yes, and it's a very cheap operation (update the target directory to include the new file/directory).
Co-Op Copying doesn't retain history, moving does.
Darcs No. Copies of files and directory structures are not supported.
Fortress No, copies are supported, but will start their own history.
Fossil Copying is not directly supported. Duplicating the file and adding it to the tracking would not copy the original file's history.
Git No. Copies are not supported.
LibreSource Synchronizer No, copies will start their own history.
Mercurial Yes. Copies are supported
Monotone No. "Tracked" copies are currently not supported, i.e. monotone does not track information about copied files.
OpenCM No. Copies are not supported.
Perforce Yes, fully supported with full history.
PureCM Yes. Copies are supported.
SourceAnywhere Copying doesn't retain history, moving does.
Subversion Yes. And it's a very cheap operation (O(1)) that is also utilized for branching.
Superversion No. Copies are not supported.
Surround SCM No. Copies are not supported.
svk Yes. Same as subversion.
Team Foundation Server Yes - you can create a branch. But the GUI has no option to view the old history. The Power-Tool tfpt has the option /followbranches to show the history of the file branch's ancestors
Vault No, copies are supported, but will start their own history.
Vesta Yes. A new package/branch can be based on any existing version without affecting the past history. (This is also an O(1) operation.)
Visual SourceSafe Yes. Copies are supported up to a point.

Remote Repository Replication

Does the system support cloning a remote repository to get a functionally equivalent copy in the local system? That should be done without any special access to the remote server except for normal repository access.

CVS That used to be the case indirectly, by using CVSup by John Polstra (which requires running the cvsupd daemon on the server). However, cvsupd has become unmaintained, now has problems with CVS 1.12.13, and is written in Modula-3, which makes it non-recommended.
AccuRev Yes.
Aegis Yes.
AllChange No.
Arch Yes.
Bazaar Yes.
BitKeeper Yes.
ClearCase Not really applicable for clearcase, but see next point.
CM+ Yes. CM+MultiSite can be configured to clone a repository so that it continues to act as a single repository. Options include cloning only from the main site (i.e. not allowing updates from the clone) and restricting the set of files transferred to a cloned site.
CMSynergy Yes, as long as you have the (more expensive) Distributed package.
Co-Op Repositories are always replicated on local machines. There is no central server.
Darcs Yes.
Fortress No.
Fossil Yes. Entire repository can be downloaded without special permission (the copy will not track upstream changes). More traditional cloning requires authorization (this is typically provided to 'anonymous' users).
Git Yes. Using the "git clone" command.
LibreSource Synchronizer Yes, but is not documented and its based on the dataflow feature of the LibreSource Synchronizer.
Mercurial Yes.
Monotone Yes.
OpenCM No.
Perforce Yes. Via the Perforce Proxy (P4P) tool, and full repository replacion.
PureCM Yes. Using the PureCM Proxy Server.
SourceAnywhere Not directly possible with the included GUI or command line tools; Some SQL Server tool might be useable.
Subversion Indirectly, either by using the svnsync tool which is part of the Subversion distribution on recent versions, or by using Chia-liang Kao's SVN::Mirror add-on or Shlomi Fish's SVN-Pusher utility.
Superversion Yes.
Surround SCM Yes, using the proxy server.
svk Yes.
Team Foundation Server TFS Proxy is available but the replica isn't an equivalent copy.
Vault No.
Vesta Yes. Replication is a fundamental part of the design.
Visual SourceSafe Not directly possible with the included GUI or command line tools; ssarc and ssrestor might be useable

Propagating Changes to Parent Repositories

Can the system propagate changes from one repository to another?

CVS No.
AccuRev With AccuReplica, the replica server has all the meta-data and fetches file data as needed by replica users; all write operations pass automatically from the replica to the master server.
Aegis Yes.
AllChange No.
Arch Yes.
Bazaar Yes.
BitKeeper Yes.
ClearCase Yes, using Clearcase Multisite.
CM+ Yes. In CM+MultiSite, changes made at the slave are, by default, propagated to the Main(master) library, as well as to all other Clones (slaves). You may also propagate changes between unrelated repositories containing some of the same source.
CMSynergy Yes, as long as you have the (more expensive) Distributed package.
Co-Op It's a peer-to-peer system, which keeps all replicas of the repository in sync.
Darcs Yes.
Fortress No
Fossil Yes.
Git Yes, it is possible.
LibreSource Synchronizer Yes, it's what we call a dataflow.
Mercurial Yes.
Monotone Yes.
OpenCM No.
Perforce Yes, via remote depots.
PureCM No.
SourceAnywhere Not directly possible with the included GUI or command line tools; Some SQL Server tool might be useable.
Subversion Yes, using either Chia-Ling Kao's SVN::Mirror script or the svn-push utility by Shlomi Fish.
Superversion No.
Surround SCM Yes.
svk Yes.
Team Foundation Server No.
Vault No
Vesta Yes.
Visual SourceSafe Not directly possible with the included GUI or command line tools; ssarc and ssrestor might be useable

Repository Permissions

Is it possible to define permissions on access to different parts of a remote repository? Or is access open for all?

CVS Limited. "pre-commit hook scripts" can be used to implement various permissions systems.
AccuRev Yes. Access can be defined per stream (branch) using access control lists.
Aegis Yes. Aegis relies on the UNIX permissions system to implement permissions for files in the repository.
AllChange Yes. Permissions may be defined based on role and area of the repository
Arch Yes. It is possible to define permissions on access to different parts of a remote repository based on the permission systems of the underlying protocol.
Bazaar Basic access control can be implemented through a contributed hook script. ACL support for the Bazaar server is planned.
BitKeeper FILL IN
ClearCase Yes, a unix-like permissions model is used, which maps onto Windows domain-based authentication in multi-platform environments.
CM+ Yes. Permissions are defined by data, primarily, not by location. If location is a part of the data, it may be used to define permissions by location. Permissions may apply to a branch, file, problem report, test case, etc. Access may be extended based on peer group, manager, and access lists.
CMSynergy No, though a single server can serve many repositories.
Co-Op First access (joining the project) requires administrator's approval. Subsequent access to that project is not controlled.
Darcs No.
Fortress Yes. Revisions can be set, and overridden, and the repository, project and folder level.
Fossil Permissions are set for the whole repository.
Git See contrib/hooks/update-paranoid that ships with Git. See the path_rules code for the closest equivalent to svnperms.
LibreSource Synchronizer Permissions are set for the whole repository or branch.
Mercurial Yes. It is possible to lock down repositories, subdirectories, or files using hooks.
Monotone Current monotone has specific read permissions with which you can control the access to certain parts (aka branch patterns) for known user ids, but less specific write permissions. Basically, if a user is allowed to write to a server, they can write everything there pretty much unrestricted.
OpenCM Permissions are defined on a per-branch basis.
Perforce Yes. (more than half a dozen of permission levels that can be set in a file by file basis)
PureCM Yes. Permissions can be set against repositories, streams (branches/labels), folders and files using Access Control Lists.
SourceAnywhere Yes. SourceAnywhere Server Manager can define access to a repository per user or group and user access rights to a project.
Subversion Yes. The WebDAV-based service supports defining HTTP permissions for various directories of the repository.
Superversion No.
Surround SCM Yes. Permissions can be defined at all levels of the system.
svk Same as subversion.
Team Foundation Server Yes. You get set permissions for each team project, folder, file.
Vault Yes. Revisions can be set, and overridden, and the repository, project and folder level.
Vesta Yes. Access permissions for each package (the unit of checkout/checkin) can be different. Access permissions for a branch can be different from the basis package.
Visual SourceSafe Project specific permissions (read, write, delete, destroy) can be set per user; but see "Networking Support": this makes "Repository Permissions" a hindrance to accidental damage but cannot prevent intentional damage.

Changesets' Support

Does the repository support changesets? Changesets are a way to group a number of modifications that are relevant to each other in one atomic package, that can be cancelled or propagated as needed.

CVS No. Changes are file-specific.
AccuRev Yes, AccuRev provides robust functionality for change sets (called change packages in AccuRev) including viewing differences by change packages and merging changes from stream to stream by change package.
Aegis Yes. Changesets are supported.
AllChange Partial. Changes may be associated with Change Requests and promoted /baselined/released as a set.
Arch Yes. Changesets are supported.
Bazaar Yes. Changesets are supported.
BitKeeper Yes. Changesets are supported.
ClearCase Not supported in this way. Extensive branching support gives similar benefits. (eg each changeset can be given a branch). Also optional UCM feature gives something like this (each changeset is a "stream").
CM+ Yes. Change packages are known as updates. By default, an update is required to make any change. The update may be checked-in, differenced, promoted, retrieved, propagated, yanked (i.e. removed from history), etc. each in a single operation. Baseline alignment is performed based on the status (i.e. promotion level) of the update. Updates also record changes to directory structure: move, add, remove.
CMSynergy Yes. Changesets (or tasks) are fundamental to the way Synergy works.
Co-Op Yes. Changesets are the default.
Darcs Yes. Changesets are supported.
Fortress Yes. Changesets are supported.
Fossil Not directly. Changeset information is available in "manifest" files but no commands are provided to automate changeset operations.
Git Yes, Changesets are supported, and there's some flexibility in creating them.
LibreSource Synchronizer Partial support. There are implicit changeset that are generated on each commit.
Mercurial Yes. Changesets are supported.
Monotone Yes. Changesets are supported.
OpenCM Yes. Changesets are supported.
Perforce Yes. Changesets are supported.
PureCM Yes. Changesets are supported.
SourceAnywhere Not exactly. SourceAnywhere uses a related concept of configurations instead, which some has similar properties.
Subversion Partial support. There are implicit changeset that are generated on each commit.
Superversion Partial support. Changes are grouped into changesets, but cannot be cancelled invididually yet.
Surround SCM Yes. Changesets (called changellists) as well as labels are fully supported.
svk Same as subversion.
Team Foundation Server Yes. Changesets are the only possibility.
Vault Yes. Changesets are supported.
Vesta Not exactly. Vesta uses a related concept of configurations instead, which some has similar properties.
Visual SourceSafe No. Changes are file-specific.

Tracking Line-wise File History

Does the version control system have an option to track the history of the file line-by-line? I.e., can it show for each line at which revision it was most recently changed, and by whom?

CVS Yes. cvs annotate
AccuRev Yes. Available from both the gui and cli.
Aegis Yes. aeannotate
AllChange Yes
Arch Not in the command line client, but ViewARCH, a web-interface for Arch, has it.
Bazaar Yes. (bzr annotate).
BitKeeper Yes. (bk annotate)
ClearCase Yes, "cleartool annotate"
CM+ Yes. View revision tags.
CMSynergy Probably, if you're a sufficiently proficient hacker with their scripting language.
Co-Op Not directly, but it's possible to compare any two versions using a visual differ.
Darcs Yes. (darcs annotate)
Fortress Yes. Both standard Blame and Line History (Blame on selected sections of a file) are supported.
Fossil Yes. This capability is provided with the 'fossil annotate' command as well as through the built-in web interface.
Git Yes. (git blame).
LibreSource Synchronizer Yes, locally without any server connection with the standard graphical Java client.
Mercurial Yes. (hg annotate)
Monotone Yes. (mtn annotate)
OpenCM Unknown. Probably not.
Perforce Yes, an annotation feature is present.
PureCM Yes, annotation is available through the GUI.
SourceAnywhere Yes. (SAW annotate)
Subversion Yes. (svn blame)
Superversion No.
Surround SCM No.
svk Yes. (svk blame)
Team Foundation Server Yes. (tf annotate).
Vault Yes. Both standard Blame and Line History (Blame on selected sections of a file) are supported.
Vesta No, but it would be easy to implement a tool that did this, as the Vesta repository provides direct filesystem access to all versions.
Visual SourceSafe Not directly, but it's possible to compare any two versions using a visual differ.

Features

Ability to Work only on One Directory of the Repository

Can the version control system checkout only one directory of the repository? Or restrict the check-ins to only one directory?

CVS Yes.
AccuRev Yes. AccuRev provides functionality to define feature streams in which only the subset of code is seen. A group of developers can then be retricted to work only from that stream so they are only allowed to check in changes to that subset of code.
Aegis No. All changes are made repository-wide.
AllChange Yes. Any arbitrary set of files or directories may be checked out or in.
Arch It is possible to commit only a certain directory. However, one must check out the entire repository as a whole.
Bazaar For checkouts: No. For checkins: Yes.
BitKeeper No. All changes are made repository-wide.
ClearCase Yes, using snapshot view load rules.
CM+ Yes. Any arbitrary set can be checked out and worked on. Similarly, arbitrary restrictions may be applied for check-in, including file ownership.
CMSynergy Yes and no. Files and directories are checked out and in individually, however you have to work in the context of a project, which consists of one or more directories.
Co-Op No. All changes are made to a project as a unit, but it's possible to access each file's history separately.
Darcs It is possible to commit only a certain directory. However, one must check out the entire repository as a whole.
Fortress Yes.
Fossil No. Checkouts are of the entire repository, however, commits can be limited to any subset of files (e.g., just the contents of a subdirectory).
Git No. However, commits could be restricted somewhat, see the "Repository Permissions" item.
LibreSource Synchronizer It is possible to commit only a certain directory. However, one must check out the entire repository as a whole.
Mercurial It is possible to commit changes only in a subset of the tree. There are plans for partial checkouts.
Monotone It is possible to commit changes only in a subset of the tree. However, one must extract the entire tree to work on it.
OpenCM No. All changes are made to a project as a unit
Perforce Yes. Changes to a sub-directory of the repository are supported.
PureCM Yes.
SourceAnywhere Yes. SourceAnywhere can define the user access right to each project and users can be restricted to work only on the projects they have check out/in right.
Subversion Yes.
Superversion No.
Surround SCM Yes.
svk Yes.
Team Foundation Server Yes.
Vault Yes.
Vesta Yes and no. The unit of checkout/checkin (called a package) is a directory tree. Most projects use more than one. Once created, a package must be checked out/in as a unit.
Visual SourceSafe Yes.

Tracking Uncommited Changes

Does the software have an ability to track the changes in the working copy that were not yet committed to the repository?

CVS Yes. Using cvs diff
AccuRev Yes. The functionality is available through both the GUI and the command line interface.
Aegis Yes. Using aediff.
Aegis Yes. Using aediff.
AllChange Yes. Using the comparison facilities.
Arch Yes, using "tla changes".
Bazaar Yes, using "bzr diff".
BitKeeper Yes. Using "bk diffs".
ClearCase Yes, "cleartool diff".
CM+ Yes. Use Updates | Delta | Delta Update. Or right click a file or directory and do a compare to workspace.
CMSynergy Yes, either using the integrated diff tool or a user-configured external diff tool.
Co-Op Yes, using built-in visual differ/editor.
Darcs Yes, using "darcs whatsnew".
Fortress Yes. Using DiffMerge.
Fossil Yes. Using 'fossil diff' or 'fossil gdiff'. Tracking status of all files is also available.
Git Yes. Also, branches are very lightweight in Git, and could be considered a kind of storage for "uncommitted" code in some workflows. Also see the "git stash" command.
LibreSource Synchronizer Yes, with the Synchronizer Studio (default Java client) or with the standard diff command (diff -r . .so6/xxx/REFCOPY/)
Mercurial Yes. Using hg diff.
Monotone Yes. In a similar fashion to CVS.
OpenCM Yes. Using cm diff
Perforce Yes.
PureCM Yes.
SourceAnywhere Yes. Using saw diff.
Subversion Yes. Using svn diff.
Superversion Yes. Local changes are detected and shown immediately. Changes can be collected in a local buffer before being committed to the repository.
Surround SCM Yes, using the repository difference.
svk Yes. Using svk diff.
Team Foundation Server Yes. Using tf diff or "Pending Changes" in Visual Studio.
Vault Yes. Using DiffMerge.
Vesta Yes. Intermediate immutable snapshots can be taken during an active checkout (with vadvance). These intermediate versions can be treated just like checked in versions: they can be replicated to other repositories and used as the basis for branches.
Visual SourceSafe Yes, using the integrated diff tool.

Per-File Commit Messages

Does the system have a way to assign a per-file commit message to the changeset, as well as a per-changeset message?

CVS No. Commit messages are per change.
AccuRev No. Commit messages are per change.
AllChange No. Commit messages are per check in.
Arch No.
Bazaar With respect to pure Bazaar: No. At least one plugin (bzr-gtk) supports it though.
BitKeeper Yes. It is possible to have a per-file commit message.
ClearCase Yes, assuming a comment on the branch is sufficient for a per-changeset message.
CM+ Yes. Out of the box CM+ is configured to prompt for messages (i.e. comments) only per change. However, the schema is pre-configured so that you may prompt on a per file basis as well (typically done at checkout time as the entire change is normally checked in with a single operation.
CMSynergy Yes.
Co-Op No. Commit messages are per change. They go to all project members and update their repositories.
Darcs No.
Fortress No. Commit messages are per-changeset.
Fossil No. Commit messages are per check in.
Git No. Commit messages are per changeset.
LibreSource Synchronizer No. Commit messages are per changeset.
Mercurial No.
Monotone No. Commit messages are per-changeset.
OpenCM Unknown.
Perforce No. Commit messages are per change.
PureCM No. Commit messages are per change.
SourceAnywhere No. There is no such feature.
Subversion No. There is no such feature.
Superversion Yes.
Surround SCM Yes.
svk No. There is no such feature.
Team Foundation Server No. Commit messages are per changeset.
Vault No. Commit messages are per-changeset.
Vesta Not exactly. The unit of checkin is a directory, and commit messages are assigned at that level, not to individual files. Since configurations are also versioned, they also have commit messages.
Visual SourceSafe Since changesets are not supported, yes.

Technical Status

Documentation

How well is the system documented? How easy is it to get started using it?

CVS Excellent. There are many online tutorials and resources and an online book. The command line client also provides an online comprehensive help system.
AccuRev Excellent. There is a full set of documentation available in pdf format available at AccuRev Documentation as well as context-sensitive help in the GUI.
Aegis Medium. The documentation is given in several large scope troff documents, that are only usable as not-so-PDFish PDF documents, and as text documents that lack any formatting. It is very hard to get started using it with the online resources. The content is of good quality, but otherwise not made very accessible.
AllChange Excellent. There is a full set of documentation available as both help and PDF.
Arch Medium. There are two online tutorials and a comprehensive online documentation. The command line client also supplies a reference page. However, some of the documentation is out of date or incomplete.
Bazaar Excellent. Apart from online help in the command line client there exist tutorials, a reference card ("Quick Start Guide"), several full fledged guides and references, and documents on specialized topics, such as migration from other VCS systems and different workflows. The documentation comes in html and plain-text formats. The API of the underlying library is fully documented. In the UI design of the command line client special attention was paid to make it easy to get started with Bazaar.
BitKeeper Very good. There is a comprehensive help at the BitKeeper site. Each command is documented in its own man page, and the client contains a help tool that offers an integrated help system.
ClearCase Extensive online help in Windows Help / UNIX manpage format, also PDF-based documentation. However the complexity of the tool can mean a lengthy ramp-up time.
CM+ Very good. There is a self-demo/tutorial to get you started quickly. Administration is minimal. So normal developer use requires only a 1 to 2 hour training session (or equivalent guide) to introduce you to concepts and capabilities (e.g. like updates, options). Customization documentation is also extensive but should normally be accompanied by a 2-day to 4-day course for GUI, Process, Data and Application set customization.
CMSynergy Medium. Lots of books, plus somewhat clunky set of HTML pages, but has some radical concepts which can cause real problems really quickly. They recommend a day's training for basic users, more for more advanced users. Took a while to become fluent.
Co-Op Very good. Step-by-step tutorial and HTML help is included.
Darcs Good. The manual contains a brief tutorial and a solid reference. Every sub-command can print its usage. Because the command-set is small and the model is simple, many users find it easy to get started.
Fortress Good. All features are documented, plus a getting-started guide.
Fossil Fossil is well documented. Manpage-type help is available for all commands using 'fossil help'. Fossil also includes a built-in web interface permitting easy visual exploration and administration. There are also tutorials, user guides, and a wiki available on the Web.
Git Good. There's an online help for every command detailing all the flags. The man pages are extensive, but tended to be confusing (possibly improved by now). There are many tutorials, blog posts and some books (some of which are online).
LibreSource Synchronizer Medium. There are an online tutorial and some comprehensive online documentation. Installing and getting started with the GUI is very easy though. (update/commit-next-next-next-finished)
Mercurial Very good. There is a companion book and a wiki. Every command has integrated help.
Monotone Good. There's a lot of documentation available in PDF and HTML formats. The client supplies documentation for every command.
OpenCM Well documented.
Perforce Very Good (HTML and command line help).
PureCM Very Good (HTML and command line help).
SourceAnywhere Good. There's an overview and tutorial on the web site, and integrated help for every command.
Subversion Very good. There is a free online book and some online tutorials and resources. The book is written in DocBook/XML and so is convertible to many different formats. The command-line client also provides a good online help system that can be used as a reference.
Superversion Fairly poor. There are two tutorials, but there is no reference. Installing and getting started with the GUI is very easy though.
Surround SCM Excellent. There is a full set of documentation available as both help and PDF.
svk Relatively poor, but improving. There's a work-in-progress book as well as the Wiki and some external Articles and Tutorials.
Team Foundation Server Good. A comprehensive documentation in the MSDN Library. Many Step-by-Step tutorial videos online.
Vault Good. All features are documented, plus a getting-started guide.
Vesta Quite thoroughly (HTML, man pages, published papers, a book-length research report).
Visual SourceSafe Medium. Help file which is sometimes useful. However, the interface is reasonably intuitive so documentation isn't needed as much.

Ease of Deployment

How easy is it to deploy the software? What are the dependencies and how can they be satisfied?

CVS Good. Out of being the de-facto standard, CVS is available on most systems and is easy to deploy.
AccuRev Excellent. All that is required is to download the binaries for the appropriate platform and run the installer. The installation package is self-contained. No additional software is needed. AccuRev supports most UNIX, Linux, and Windows platforms and deploying AccuRev to a multi-platform environment is straight-forward.
Aegis The Aegis binary should be installed as SUID-root, and so requires root privileges to install. It also not very portable to Win32 systems. Other than that, Aegis supports an easy autoconf or RPM/apt-based installation process.
AllChange Good. Various out-of-the-box configurations supplied including ITIL support. These may be tailored or used as is. Time to deploy depends on how much configuring is done.
Arch Excellent. An arch service is nothing but a filesystem-space hosted by any of its supported protocols (FTP, SFTP, WebDAV, etc.). The arch client is written in C, and is portable across UNIX systems (and on Win32 only with a UNIX emulation layer).
Bazaar Very easy. Bazaar has an installer for MS Windows and packages for some major Linux distributions, FreeBSD, and Mac OS X. The dependencies for manual installation are listed on the Bazaar website.
BitKeeper Good. All that is required is downloading a binary for the system and installing it using the installation script. The package is self-contained and is easy to set up.
ClearCase Poor. Clearcase is very difficult to install in general. At least, setup for a new site is quite complex. Installing additional servers (eg repository servers) is less so.
CM+ Yes. Typical installation need only be done on the server (with a single shortcut established on the client). This assumes file system connectivity. For IP only connectivity, installation is also required on remote clients. Installation is typically a couple of minutes. No dependencies unless web interface is used, in which case an Apache server is required. A download is available from Neuma's web site and takes you right into a self-guided fully working demo version.
CMSynergy Medium. There is a detailed install guide for setting it up using a binary kit and a set of scripts. However it still took several tries to get it properly installed and configured. The Windows client has a slightly clunky Windows installer.
Co-Op Very easy to deploy, since there is no central server. Can be configured to use e-mail or LAN (or both) for synchronization. For e-mail, requires MAPI-compliant e-mail client.
Darcs Very good. darcs requires few external libraries, however you need the Glasgow Haskell Compiler if you cannot find a binary. To start working, just "darcs init".
Fortress Easy. Prerequisites are IIS 5 or higher, SQL 2000 or higher. Install takes minutes.
Fossil Fossil is a single, stand-alone executable file that can be installed anywhere in the user's execution path. Precompiled binaries are available for GNU/Linux, Windows, and Mac OS X. Fossil only has the ZLIB compression tools library as its only dependency.
Git Good. Binary packages are available for modern platforms. C compiler and Perl are required. Requires cygwin on Windows, and has some UNIXisms.
LibreSource Synchronizer Excellent. It is managed by JavaWebStart with links on any LibreSource repository web page. (links: create workspace, update, commit, studio...)
Mercurial Excellent. Binary packages are available for all popular platforms. Building from source requires only Python 2.3 (or later) and a C compiler.
Monotone Excellent. It is possible to copy or compile the executable to the user's machine, without any configuration or external dependencies.
OpenCM Very good. Install the RPM, or build from tarball and install the init script.
Perforce Very good. Perforce is very easy to deploy.
PureCM Very good. PureCM is very easy to deploy.
SourceAnywhere Excellent. Dynamsoft SourceAnywhere is extremely easy to install. It is totally written in C++ from scratch, which means that you don't need any additional components and frameworks to support the installation.
Subversion A Subversion service requires installing an Apache 2 module (if one wishes to use HTTP as the underlying protocol) or its own proprietary server. The client requires only the Subversion-specific logic and the Neon WebDAV library (for HTTP). Installation of the components is quite straightforward, but will require some work, assuming Subversion does not come prepackaged for one's system.
Superversion If Java 1.4 is installed, deployment of Superversion usually takes two clicks.
Surround SCM Excellent. All that is required is to download the binaries for the appropriate platform and run the installer. The installation package is self-contained. No additional software is needed. Surround SCM supports Windows, Mac OS X, Linux, and Solaris platforms and deploying Surround SCM to a multi-platform environment is straight-forward.
svk In addition to installing subversion, users are required to install the subversion perl bindings and a few modules from CPAN.
Team Foundation Server Installation is quite complex. Needs IIS, MS-SQL Server and Reporting Services. A own installation guide with step-by-step guide is available. Allows separating in data and app tier.
Vault Easy. Prerequisites are IIS 5 or higher, SQL 2000 or higher. Install takes minutes.
Vesta Medium to Good. There is a detailed installation guide for setting it up using a binary kit. RPMs and Debian packages have been recently released. There are no dependencies on other software. There is a bootstrap package available to build Vesta from using "make".
Visual SourceSafe Very good - an installation package which does the work. When you create a repository it installs the exe's in a directory and you can run them from there if you need to.

Command Set

What is the command set? How compatible is it with the commands of CVS (the current open source defacto standard)?

CVS A simple command set that includes three most commonly used commands (cvs commit, cvs update and cvs checkout) and several others.
AccuRev Very extensive but not compatible with cvs.
Aegis A complex command set that involves many operations just to get started. Not CVS-compatible. (albeit support for such basic operations was contemplated) Note that Aegis is a Software Configuration Management system and not just a simple version control system, which may justify this extra complexity.
AllChange Very extensive but not compatible with cvs.
Arch Many commands are compatible with CVS or BitKeeper. However, there are many other commands for it for different uses. Aliasing of commands is possible so it it may be possible to make it more compatible.
Bazaar Tries to follow CVS conventions, but deviates where there is a different design.
BitKeeper A CVS-like command set with some easy-to-get-used-to complications due to its different way of work and philosophy.
ClearCase Excellent. All tools are available through the command-line. Not very compatible with CVS though.
CM+ CM+ has several dozen commands that can be used both for operation and configuration of the product. As CM+ is change-based, commands are substantially different than CVS. The GUI is used primarily and implemented on top of the command set. As well, CM+ covers a full ALM suite and can be extended beyond, so there are many more generic commands for browsing, reporting, etc.
CMSynergy An extensive and powerful command set, which has some CVS similarity, though the architecture is so different that it quickly moves away for anything but the basics.
Co-Op Basic commands are compatible with CVS.
Darcs The command set is fairly compact and the core commands are easy to understand. Follows CVS in a few places, but since the model is different most commands are unique.
Fortress Extensive command set via command line and GUI. Not compatible with CVS.
Fossil Basic command set with most core commands identical to CVS (though the option switches are often different).
Git Command set is very feature-rich, and not compatible with CVS.
LibreSource Synchronizer Basic commands available (commit/update), but it's really simple to use the GUI. Ant task are also available.
Mercurial Tries to follow CVS conventions, but deviates where there is a different design.
Monotone Tries to follow CVS conventions, but deviates where there is a different design.
OpenCM A CVS-like command set that is familiar to existing CVS users.
Perforce Very extensive but not compatible with CVS.
PureCM A CVS-like command set which is easy to get used to for CVS-users.
SourceAnywhere Very extensive but not compatible with CVS.
Subversion A CVS-like command set which is easy to get used to for CVS-users.
Superversion There is little need to memorize a command set because all actions take place in a GUI. A part of the terminology used in the application is borrowed from CVS.
Surround SCM Very extensive but not compatible with cvs.
svk A CVS-like command set which is easy to get used to for CVS-users.
Team Foundation Server The command set allows more operations than the GUI but isn't compatible with CVS.
Vault Extensive command set via command line and GUI. Not compatible with CVS.
Vesta The command set is unrelated to CVS. Most of the time, users use about 5 commands. Few ever need to know more than about 20 commands.
Visual SourceSafe A bit of an afterthought. It's possible to do basic things, but it's really geared up for using the GUI.

Networking Support

How good is the networking integration of the system? How compliant is it with existing protocols and infra-structure?

CVS Good. CVS uses a proprietary protocol with various variations for its client/server protocol. This protocol can be tunneled over an SSH-connection to support encryption.
AccuRev Good. (proprietary protocol using TCP/IP)
Aegis Poor. Aegis is filesystem-oriented and so can be networked only via NFS (network file-system) or a similar protocol. There exists some HTTP-functionality, but it is quite limited.
AllChange Good. Uses TCP/IP and HTTP/HTTPS
Arch Excellent. Arch can utilize a multitude of protocols for its service, which is nothing but a dumb remote filesystem server. Currently supported protocols include FTP, SFTP, WebDAV (remote file access over HTTP), as well as any remote filesystem protocol (NFS, SMB).
Bazaar Excellent. Works natively over HTTP (read-only), FTP and SFTP without having Bazaar installed at the remote end. Works over HTTP, SSH and a custom protocol when talking to a remote Bazaar server. Supports RSYNC and WebDAV (experimental) through plugins.
BitKeeper Good. Repositories can be checked out from remote over HTTP, and BitKeeper also sports its own proprietary protocol for communicating between one repository and the other.
ClearCase Poor. Uses an *extremely* chatty RPC protocol for most clearcase operations, plus NFS or SMB for accessing the files themselves. Typically servers should be deployed locally (ie on the same LAN) as the client workstations for acceptable performance.
CM+ Very good. File system connectivity, TCP/IP connectivity and Web connectivity may be intermixed. MultiSite connectivity is over TCP/IP, as is License server. Works well with SSH, NFS, SMB, etc.
CMSynergy Good (single TCP/IP socket)
Co-Op Uses the simplest LAN interface: copying files between shared directories.
Darcs Good. Darcs supports getting patches over HTTP, and getting and sending patches over SSH and email.
Fortress Good. HTTP and HTTPS only.
Fossil Excellent. Fossil integrates both server and client into a single application. A built-in webserver permits graphical administration and navigation over HTTP and HTTPS; as well as providing a bug ticketing system and a simple wiki for documentation.
Git Excellent. Can use the native Git protocol, but also works over rsync, ssh, HTTP and HTTPS.
LibreSource Synchronizer Good. Use of HTTP to get through firwalls.
Mercurial Excellent. Uses HTTP or ssh. Remote access also works safely without locks over read-only network filesystems.
Monotone Good. Uses a custom protocol called "netsync".
OpenCM Good. Uses its own proprietary client/server protocol.
Perforce Good. (single TCP/IP socket)
PureCM Good. (single TCP/IP socket)
SourceAnywhere Good. (single TCP/IP socket)
Subversion Very good. The Subversion service can use either WebDAV+DeltaV (which is HTTP or HTTPS based) as its underylying protocol, or its own proprietary protocol that can be channeled over an SSH connection.
Superversion Good. Network support based on RMI is integrated seamlessly. Encryption and HTTP tunnelling are planned for the near future.
Surround SCM Good. (proprietary protocol using TCP/IP)
svk Very good. svk uses SVN::Mirror to retrieve remote repository. There has been plans to add VCP support to SVN::Mirror so it will be able to mirror from arbitary remote version control systems.
Team Foundation Server Good. Use of HTTP(S).
Vault Good. HTTP and HTTPS only.
Vesta Networking is inherent to the system. The repository exports both an NFS interface and an RPC interface. The checkout and checkin tools automatically contact a remote repository when required to perform an operation.
Visual SourceSafe VSS uses a Windows network share which has to be writable for the VSS users (since this means doubling maintenance for new users). Add user in VSS and to share permissions. the share is most often world-writable, as is the default when creating a share) It does not perform well over a slow network connection.

Portability

How portable is the version-control system to various operating systems, computer architectures, and other types of systems?

CVS Good. Client works on UNIX, Windows and Mac OS. Server works on UNIXes and on Windows with a UNIX emulation layer.
AccuRev Excellent. The server runs on most UNIX, Linux and Windows platforms. The client runs on all of these platforms and on Mac OS X.
Aegis Medium. The source is portable across all UNIXes, but the Windows version work only using cygwin, and even then not entirely natively.
AllChange Available only for windows platforms.
Arch Good. The source is portable across all UNIXes, but requires a UNIX emulation layer on Windows. (need to verify). A service can be hosted on any platform that sports a suitable Internet service.
Bazaar Works on MS Windows, Linux, Mac OS X, FreeBSD, UNIX, and basically on any system that has a recent Python port. With case-insensitive file systems there are some issues that can be avoided by using a graphical frontend. On MS Windows there is a plugin to support tracking of symlinks even if they are not supported natively by the file system.
BitKeeper Very good. Binaries are available for most common UNIX systems and for Windows 98 and above.
ClearCase Medium. Available on Windows, and several selected flavours of UNIX (not including any other Linux distribution than some versions of Red Hat Enterprise Linux, SUSE Liunx Enterprise Desktop and Ubuntu Linux).
CM+ Good. Clients and Servers work on Unix, Linux, and Windows. MAC OS X port pending. Moving server from one platform to another is a copy operation only. Can have different platforms for different servers in a MultiSite configuration. Easily configurable Web client also supported. No CR/LF issues. Scripts are all portable as well.
CMSynergy Very good - various flavours of Unix, Windows (only NT family for the server), VMS, and possibly other systems.
Co-Op Windows only: starting with Win95.
Darcs Very good. Supports many UNIXes, Mac OS X, and Windows, and is written in a portable language.
Fortress The server, and standalone client, are Windows only. The Eclipse plugin is cross-platform, as is the command-line client.
Fossil Fossil integrates both server and client into a single application which can run on any POSIX-like operating system (e.g., GNU/Linux, Mac OS X, MS Windows, et al).
Git The client works on most UNIXes, and there's a native MS-Windows build. The cygwin build seems to be workable as well.
LibreSource Synchronizer Excellent. Clients and servers work on any Java 1.5-compatible platform. (Windows, Linux and Mac OS X )
Mercurial Excellent. Runs on all platforms supported by Python. Repositories are portable across CPU architectures and endian conventions.
Monotone Excellent. Executable is portable across all UNIXes and Win32.
OpenCM Good. Portable across all UNIX systems.
Perforce Excellent. Runs on UNIX, Mac OS, BeOS and Windows.
PureCM Excellent. Client and Server run on Windows, Linux, Solaris and other UNIXes. The client also runs on Mac OS X.
SourceAnywhere Good. The server runs on Windows only. Clients can work on any platform that SWT (Standard Widget Toolkit) supports, including Windows, Linux, Mac, Solaris, AIX, HP-UX, SCO Unix, FreeBSD and so on.
Subversion Excellent. Clients and Servers work on UNIX, Windows and Mac OS X.
Superversion Excellent. Clients and servers work on any Java 1.4-compatible platform. There is official support for Windows, Linux and OS/2.
Surround SCM Excellent. The server runs on Windows, Mac OS X, Linux and Solaris platforms. The client runs on all of these platforms.
svk Good. Clients requires subversion and its perl bindings.
Team Foundation Server The Server and Client needs Windows. A thirdparty company, Teamprise, has developed a client for Eclipse, which means Linux, Mac and other UNIXes support. The Project SvnBridge allows access using SVN clients but needs to run on Windows.
Vault The server, and standalone client, are Windows only. The Eclipse plugin is cross-platform, as is the command-line client.
Vesta Good. It should be portable to any UNIX system. Currently it runs on Digital/Compaq/HP Tru64 UNIX and Linux on several different CPU architectures. Ports to Solaris and FreeBSD are planned but haven't begun yet.
Visual SourceSafe The Microsoft Product is Windows only. MainSoft ships a version of it for some UNIX platforms.

User Interfaces

Web Interface

Does the system have a WWW-based interface that can be used to browse the tree and the various revisions of the files, perform arbitrary diffs, etc?

CVS Yes. CVSweb, ViewVC, Chora, and wwCVS.
AccuRev No.
Aegis Yes.
AllChange Yes.
Arch There's ViewARCH, and ArchZoom which are works in progress.
Bazaar Yes, several: Loggerhead, Webserve, Bzrweb, and Trac.
BitKeeper Yes. Its own built-in web-interface.
ClearCase Yes. Web views are supported.
CM+ Yes. Can be configured to restrict which operations are allowed by which users, so that customers may access their requests without seeing development team data.
CMSynergy Possibly.
Co-Op Since this functionality is always available locally, there is no need for web interface.
Darcs darcs.cgi is included in the distribution.
Fortress Yes.
Fossil Yes. Fossil also includes a web-based bug ticketing system and built-in wiki.
Git Yes. Gitweb is included in distribution and there's also cgit.
LibreSource Synchronizer Yes, without diff features but with a better awareness support. (allow to know at any time on each version each one is working on)
Mercurial Yes. The web interface is a bundled component.
Monotone Yes. ViewMTN and a Trac plug-in.
OpenCM No.
Perforce Yes, P4Web.
PureCM Yes.
SourceAnywhere Currently not.
Subversion Yes. ViewVC, SVN::Web, WebSVN, ViewSVN, mod_svn_view, Chora, Trac, SVN::RaWeb::Light, SVN Browser, Insurrection and perl_svn. Aside from that, the Subversion Apache service provides a rudimentary web-interface.
Superversion No.
Surround SCM Yes, using WebDAV.
svk Yes. Same as Subversion.
Team Foundation Server Web Access is available as download for free.
Vault Yes.
Vesta Yes: Vestaweb.
Visual SourceSafe It is possible to code one using the API, but no official or third-party one exists.

Availability of Graphical User-Interfaces.

What is the availability of graphical user-interfaces for the system? How many GUI clients are present for it?

CVS Very good. There are many available GUIs: WinCVS, Cervisia (for KDE), TortoiseCVS (Windows Explorer plug-in).
AccuRev A single, comprehensive, java-based GUI is provided. The GUI has the same look-and-feel on all platforms.
Aegis There is tkaegis.
AllChange A single windows based interface is provided.
Arch There are tlator, Octopy, and ArchWay and possibly others under development.
Bazaar There are several graphical frontends in development, see the Bazaar Plugins page and the Third-party Tools page. Notable are QBzr (Qt) and bzr-gtk (GTK+), which can be considered beta quality. Work is also being done on integrating Bazaar with Windows Explorer, Eclipse, Nautilus, and Meld.
BitKeeper Good. BitKeeper ships with several GUIs for performing common tasks. I'm not aware of any third-part GUIs.
ClearCase Supplied for both Windows and UNIX. GUI tools are typically not as solid as the command-line tools though.
CM+ Excellent. Windows and Unix/Linux GUI as well as web GUI. Extensively configurable via simple menu files, browser files, etc. Can customize the set of to-do lists by user/role, same for menus, pop-up menus, default visible tabbed reports, etc. GUI also used for all admin and for process and data schema customization. Also plug-in for Visual Studio, Eclipse, etc. and File Browser (Windows).
CMSynergy A couple of GUIs. A motif-based one (even on Windows) allows most functionality but is clunky. A nicer Java one allows developer work but not much administrative stuff. Has an SCCI plug-in, though it doesn't handle network problems well.
Co-Op The system is GUI-based by design.
Darcs None to speak of. (There is a modest graphical interface to a few commands in the distribution, but it is not being developed currently.)
Fortress Standalone Windows GUI, Visual Studio integration, and cross-platform Eclipse integration.
Fossil None except the built-in web-interface.
Git Gitk is included in distribution. Qgit and Git-gui tools are also available.
LibreSource Synchronizer One written in Java/SWING and available on any OS that is automatically launched from the repository web page and another one which is an Eclipse plugin.
Mercurial History viewing available with hgit extension; check-in extension (hgct) makes committing easier. TortoiseHg provides a Windows shell extension, and GNOME/Nautilus integration. Some third-party IDEs and GUI tools (e.g. eric3, meld) have integrated Mercurial support.
Monotone Yes, there is mtn-browse (which should be considered the "best of breed"), monotone-viz and guitone. There's a complete list of tools available on the Monotone wiki.
OpenCM No GUIs are available.
Perforce Yes, P4Win, P4V and others based on the available libp4 library. There are also plugins for Eclipse, Visual Studio and other environments.
PureCM Cross-platform GUI for Windows, Linux, Mac OS X and other UNIXes.
SourceAnywhere The system is GUI-based by design.
Subversion Very good. There are many available GUIs: RapidSVN (cross-platform), TortoiseSVN (Windows Explorer plug-in), Jsvn (Java), etc. Most of them are still under development.
Superversion A GUI is integrated.
Surround SCM A complete native GUI is available for all platforms.
svk No GUIs are available.
Team Foundation Server TFS client integrates into Visual Studio.
Vault Standalone Windows GUI, Visual Studio integration, and cross-platform Eclipse integration.
Vesta No GUIs are available, but the repository has a C++ API, and it is not hard to write one. (At least three different project-specific ones have been written by users at Compaq and Intel.)
Visual SourceSafe Standalone GUI comes with it, plus SCCI plug-in for MS Visual Developer Studio. There is an Eclipse plug-in.

License

What are the licensing terms for the software?

CVS GNU GPL (open source)
AccuRev Proprietary, named-user licensing.
Aegis GNU GPL (open source)
AllChange Proprietary, named-user and concurrent licensing available.
Arch GNU GPL (open source)
Bazaar GNU GPL (open source)
BitKeeper Proprietary, binary only license. Pay per use license, with an option for a costless license for developers of open source software. Used to have a gratis, downloadable license, which was intended for the develpoment of open source software. It had a problematic license, and was discontinued starting at April 2005.
ClearCase Proprietary, with floating license supported. License server contacted for each clearcase operation, which obtains a license to be used for a next duration (8 hours by default - most people lower it to 2 hours or less, while 30 minutes is the minimum). Prices are several $k per license plus a yearly maintenance fee. Typically 1-3 users per license required, depending on activity. Multisite requires additional licensing.
CM+ Network licenses and user licenses. No minimum checkout time, and automatic license checkin on idle. License server included in product. Professional and Enterprise editions. Enterprise includes customizations, additional applications, and full multiple site capability. One Server license per site. Total license cost per user typically less than $1000 + 18% annual mtce.
CMSynergy Prices negotiable with salesman. Server is typically roughly 20,000 British Pounds. Clients are 4,000 British Pounds. Per-year costs of 18% of original.
Co-Op Proprietary, short text key. 30-day full-featured trial. Free to "observers" (members who don't make changes). $159 per workstation.
Darcs GNU GPL (open source)
Fortress Commercial, per-user with no separate server license.
Fossil Simplified BSD license, also known as the BSD 2-clause license (open source).
Git GNU GPL v2 (open source).
LibreSource Synchronizer QPL - The Qt Public License (open source)
Mercurial GNU GPL (open source)
Monotone GNU GPL (open source)
OpenCM GNU GPL (open source), but moving soon to BSD or CPL (also open source).
Perforce A proprietary, binary only, commercial license. Price starting at $800 per seat for the first year and then a $160 for continuing support for the subsequent years. The latter payment is optional and required only for support, as the product can be used without it. Free for open source projects (no support in this case), and there is also a ‘free for 20 users’ offer.
PureCM A proprietary, binary only, commercial license. Price starting at $1000 for 5 users
SourceAnywhere Proprietary, named-user licensing.
Subversion Apache/BSD-style license. (open source)
Superversion GNU GPL (open source)
Surround SCM Proprietary, named and floating licensing.
svk Perl License. (open source)
Team Foundation Server Commercial license.
Vault Commercial, per-user with no separate server license.
Vesta GNU LGPL (open source)
Visual SourceSafe VSS Ships with MSDN, and can also be purchased standalone or with other tools.

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