View source for Apache Subversion

{{Short description|Free and open-source software versioning and revision control system}}
{{Lead too short|date=October 2022}}
{{Infobox software
| name                 = Subversion
| title                = Apache Subversion
| logo                 = Apache Subversion logo.svg
| author               = [[CollabNet]]
| developer            = [[Apache Software Foundation]]
| released             = {{Start date and age|2000|10|20|df=yes}}
| latest release version = {{wikidata|property|preferred|references|edit|P348|P548=Q2804309}}
| latest release date    = {{Start date and age|{{wikidata|qualifier|preferred|single|P348|P548=Q2804309|P577}}|df=yes}}
| ver layout           = stacked
| programming language = [[C (programming language)|C]]
| operating system     = {{hlist|[[Linux]]|[[FreeBSD]]|[[HP-UX]]|[[NetBSD]]|[[OpenBSD]]|[[OpenVMS]]|[[macOS]]|[[Solaris (operating system)|Solaris]]|[[Windows]]}}
| genre                = [[Revision control]]
| license              = [[Apache License|Apache-2.0]]{{efn|Apache-2.0 since 2009-07-07.}}
}}

'''Apache Subversion''' (often abbreviated '''SVN''', after its command name ''svn'') is a [[version control]] system distributed as [[Open-source software|open source]] under the [[Apache License]].<ref>{{cite web |year=2020 |title=Subversion |url=https://directory.fsf.org/wiki/Subversion#tab=Details |access-date=3 October 2023 |website=directory.fsf.org |publisher=[[Free Software Directory]] |language=en-US}}</ref> Software developers use Subversion to maintain current and historical versions of files such as [[source code]], web pages, and documentation. Its goal is to be a mostly compatible successor to the widely used [[Concurrent Versions System]] (CVS).

The [[Open-source software|open source]] community has used Subversion widely: for example, in projects such as [[Apache Software Foundation]], [[FreeBSD]], [[SourceForge]], and from 2006 to 2019, [[GNU Compiler Collection|GCC]]. [[CodePlex]] was previously a common host for Subversion repositories.

Subversion was created by [[CollabNet]] Inc. in 2000, and is now a top-level Apache project being built and used by a global community of contributors.<ref>{{Cite press release |date=2020-02-27 |title=The Apache Software Foundation Announces 20th Anniversary of Apache Subversion |url=https://www.globenewswire.com/news-release/2020/02/27/1991695/17401/en/The-Apache-Software-Foundation-Announces-20th-Anniversary-of-Apache-Subversion.html |access-date=2023-01-29 |website=GlobeNewswire News Room |language=en}}</ref>

==History==
[[CollabNet]] founded the Subversion project in 2000 as an effort to write an open-source version-control system which operated much like [[Concurrent Versions System|CVS]] but which fixed the bugs and supplied some features missing in CVS.<ref name=bookhistory /> By 2001, Subversion had advanced sufficiently to [[Self-hosting (compilers)|host its own source code]],<ref name=bookhistory>{{cite web |url=https://svnbook.red-bean.com/en/1.7/svn.intro.whatis.html#svn.intro.history |work=Version Control with Subversion (for Subversion 1.7) |title=What is Subversion? > Subversion's History |author1=Collins-Sussman, Ben |author2=Brian W. Fitzpatrick |author3=C. Michael Pilato |year=2011 |access-date=15 March 2012}}</ref> and in February 2004, version 1.0 was released.<ref>{{cite web |url=https://lwn.net/Articles/72498/ |work=Linux Weekly News |title=subversion 1.0 is released |author=Benjamin Zeiss |year=2004 |access-date=30 March 2014}}</ref> In November 2009, Subversion was accepted into Apache Incubator: this marked the beginning of the process to become a standard top-level Apache project.<ref name=SDT2011>{{cite web |url=http://www.sdtimes.com/link/33886 |title=Subversion joins forces with Apache |author=Rubinstein, David |publisher=SD Times |date=4 November 2009 |access-date=15 March 2012 |archive-url=https://web.archive.org/web/20091111000653/http://www.sdtimes.com/SUBVERSION_JOINS_FORCES_WITH_APACHE/By_David_Rubinstein/About_APACHE_and_SUBVERSION/33886 |archive-date=2009-11-11}}</ref> It became a top-level Apache project on February 17, 2010.<ref>{{cite web |url=http://subversion.wandisco.com/component/content/article/1/43.html |archive-url=https://web.archive.org/web/20110512171259/http://subversion.wandisco.com/component/content/article/1/43.html |archive-date=12 May 2011 |title=Subversion is now Apache Subversion |date=18 February 2010 |access-date=15 March 2012}}</ref>

{| class="wikitable"
|-
! Version
! Original release date
! Latest version
! Latest release date
! Status
|-
| {{Version|o|1.0}}
| 2004-02-23
| 1.0.9
| 2004-10-13
| No longer supported
|-
| {{Version|o|1.1}}
| 2004-09-29<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.1.html |title=Subversion 1.1 Release Notes |access-date=2015-09-21}}</ref>
| 1.1.4
| 2005-04-01
| No longer supported
|-
| {{Version|o|1.2}}
| 2005-05-21<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.2.html |title=Subversion 1.2 Release Notes |access-date=2015-09-21}}</ref>
| 1.2.3
| 2005-08-19
| No longer supported
|-
| {{Version|o|1.3}}
| 2005-12-30<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.3.html |title=Subversion 1.3 Release Notes |access-date=2015-09-21}}</ref>
| 1.3.2
| 2006-05-23
| No longer supported
|-
| {{Version|o|1.4}}
| 2006-09-10<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.4.html |title=Subversion 1.4 Release Notes |access-date=2015-09-21}}</ref>
| 1.4.6
| 2007-12-21
| No longer supported
|-
| {{Version|o|1.5}}
| 2008-06-19<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.5.html |title=Subversion 1.5 Release Notes |access-date=2015-09-21}}</ref>
| 1.5.9
| 2010-12-06
| No longer supported
|-
| {{Version|o|1.6}}
| 2009-03-20<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.6.html |title=Apache Subversion 1.6 Release Notes |access-date=2015-09-21}}</ref>
| 1.6.23
| 2013-05-30
| No longer supported
|-
| {{Version|o|1.7}}
| 2011-10-11<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.7.html |title=Apache Subversion 1.7 Release Notes |access-date=2015-09-21}}</ref>
| 1.7.22
| 2015-08-12
| No longer supported
|-
| {{Version|o|1.8}}
| 2013-06-18<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.8.html |title=Apache Subversion 1.8 Release Notes |access-date=2015-09-21}}</ref>
| 1.8.19
| 2017-08-10
| No longer supported
|-
| {{Version|o|1.9}}
| 2015-08-05<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.9.html |title=Apache Subversion 1.9 Release Notes |access-date=2015-09-21}}</ref>
| 1.9.12
| 2019-07-24
| No longer supported
|-
| {{Version|o|1.10}}
| 2018-04-13<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.10.html |title=Apache Subversion 1.10 Release Notes |access-date=2018-04-17}}</ref>
| 1.10.8
| 2022-04-12
| No longer supported
|-
| {{Version|o|1.11}}
| 2018-10-30<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.11.html |title=Apache Subversion 1.11 Release Notes |access-date=2018-10-31}}</ref>
| 1.11.1
| 2019-01-11
| No longer supported
|-
| {{Version|o|1.12}}
| 2019-04-24<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.12.html |title=Apache Subversion 1.12 Release Notes |access-date=2019-05-01}}</ref>
| 1.12.2
| 2019-07-24
| No longer supported
|-
| {{Version|o|1.13}}
| 2019-10-30<ref>{{cite web|title=Apache Subversion 1.13 Release Notes|url=https://subversion.apache.org/docs/release-notes/1.13.html}}</ref>
| 1.13.0
| 2019-10-30
| No longer supported
|-
|{{Version|c|1.14}}
|2020-05-27<ref>{{Cite web|title=Apache Subversion 1.14 LTS Release Notes|url=https://subversion.apache.org/docs/release-notes/1.14.html|access-date=2020-06-02|website=subversion.apache.org}}</ref>
|1.14.5<ref>{{Cite web |last=The Subversion Team |title=Apache Subversion News Archives |url=https://subversion.apache.org/news.html |access-date=2024-12-20 |website=subversion.apache.org |publisher=The Apache Software Foundation}}</ref><ref>{{Cite web |first=Daniel |last=Sahlberg |date=2024-12-08 |title=Release Announcement – [SECURITY][ANNOUNCE] Apache Subversion 1.14.5 released |series=User mailing list for Subversion |url=https://lists.apache.org/thread/jz1j48zrpryw8600n0x7kssvyq90y1fs |access-date=2024-12-08 |website=lists.apache.org |publisher=The Apache Software Foundation}}</ref><ref>{{Cite web |last=The Subversion Team |date=2024-10-08 |title=Changelog for Version 1.14.5 and earlier |url=https://svn.apache.org/repos/asf/subversion/tags/1.14.5/CHANGES |access-date=2024-12-20 |website=Apache Subversion |publisher=The Apache Software Foundation}}</ref>
|2024-12-08
|Fully supported, [[Long-term support|LTS]]
|-
|{{Version|p|1.15}}
|20XX
|1.15.0
|(Not yet released)
|In development
|-
| colspan="5" | <small>{{Version |l |show=111111}}</small>
|}
<!-- o=Old-Not-Supported; co=Old-Still-Supported; c=Latest-Stable; cp=Preview; p=Planned-Future -->

Release dates are extracted from Apache Subversion's {{code|CHANGES}} file,<ref>{{cite web |url=https://svn.apache.org/repos/asf/subversion/trunk/CHANGES |title=Apache Subversion's CHANGES file |access-date=2018-10-31}}</ref> which records all release history.

==Features==
* [[Commit (data management)|Commits]] as true [[Atomicity (database systems)|atomic operations]] (interrupted commit operations in CVS would cause repository inconsistency or corruption).
* The system maintains [[Software versioning|versioning]] for directories and some specific file [[metadata]] (see [[#Properties|Properties]]). Users can move or copy files and entire directory-trees very quickly, while retaining full revision history (as being implemented by a reference to the original object).
* Versioning of [[symbolic link]]s.
* Native support for binary files, with space-efficient binary-diff storage.
* [[Apache HTTP Server]] as network server, [[WebDAV]]/[[WebDAV#Extensions and derivatives|Delta-V]] for [[Protocol (computing)|protocol]]. There is also an independent server [[process (computing)|process]] called svnserve that uses a custom protocol over [[Internet Protocol Suite|TCP/IP]].
* [[Branching (version control)|Branching]] is implemented by a copy of a directory, thus it is a cheap operation, independent of file size.
* Natively [[client–server model|client–server]], [[Abstraction layer|layered]] [[Library (computing)|library]] design.
* Client/server protocol sends [[diff]]s in both directions.
* [[Parsing|Parsable]] output, including [[XML]] log output.
* [[Open source license]]d – [[Apache License]] since the 1.7 release; prior versions use a derivative of the Apache Software License 1.1.
* [[Internationalization and localization|Internationalized]] program messages.
* [[File locking]] for unmergeable files ("reserved checkouts").
* Path-based authorization.
* [[Language binding]]s for [[C Sharp (programming language)|C#]], [[PHP]], [[Python (programming language)|Python]], [[Perl]], [[Ruby (programming language)|Ruby]], and [[Java (programming language)|Java]].
* Full [[MIME]] support – users can view or change the MIME type of each file, with the software knowing which MIME types can have their differences from previous versions shown.
* Merge tracking – merges between branches will be tracked, this allows automatic merging between branches without telling Subversion what does and does not need to be merged.
* Changelists to organize commits into commit groups.

===Repository types===
Subversion offers two types of repository storage.

====Berkeley DB (deprecated)====
The original development of Subversion used the [[Berkeley DB]] package.
Subversion has some limitations with Berkeley DB usage when a program that accesses the database crashes or terminates forcibly. No data loss or corruption occurs, but the repository remains offline while Berkeley DB replays the journal and cleans up any outstanding locks. The safest way to use Subversion with a Berkeley DB repository involves a single server-process running as one user (instead of through a shared filesystem).<ref name="backend">
{{cite book |author1=Ben Collins-Sussman |author2=Brian W. Fitzpatrick |author3=C. Michael Pilato |title= Version Control with Subversion: For Subversion 1.7 |year= 2011 |chapter= Chapter 5: Strategies for Repository Deployment |url= https://svnbook.red-bean.com/en/1.7/svn.reposadmin.planning.html#svn.reposadmin.basics.backends | publisher = O'Reilly}}
</ref> The Berkeley DB backend was deprecated in version 1.8.<ref>{{cite web |url=https://subversion.apache.org/docs/release-notes/1.8.html#bdb-deprecated |title=Apache Subversion 1.8 Release Notes |publisher=Apache Project |access-date=5 May 2020}}</ref>

====FSFS====
{{Redirect|FSFS|the Freesat service from Sky|Freesat from Sky|the book by Richard Stallman|Free Software, Free Society}}
In 2004, a new storage subsystem was developed and named FSFS.
It works faster than the Berkeley DB backend on directories with a large number of files and takes less disk space,
due to less logging.<ref name="backend"/>

Beginning with Subversion 1.2, FSFS became the default data store for new repositories.

The etymology of "FSFS" is based on Subversion's use of the term "filesystem" for its repository storage system.
FSFS stores its contents directly within the operating system's filesystem, rather than a structured system like Berkeley DB.
Thus, it is a "[Subversion] FileSystem atop the FileSystem".

====FSX====
A new filesystem, called FSX, is under development to remove some limitations of FSFS. As of Version 1.9, it was not considered production-ready.<ref>{{Cite web|url=https://subversion.apache.org/docs/release-notes/1.9.html#fsx|title = Apache Subversion 1.9 Release Notes}}</ref>

===Repository access===
{{Main| Comparison of Subversion clients}}
Access to Subversion repositories can take place by:

# Local filesystem or network filesystem,<ref>[[Berkeley DB]] relies on file locking and thus should not be used on (network) filesystems which do not implement them</ref> accessed by client directly. This mode uses the {{mono|file:///path}} access scheme.
# [[WebDAV]]/Delta-V (over http or https) using the {{mono|mod_dav_svn}} module for [[Apache HTTP Server|Apache 2]]. This mode uses the {{mono|<nowiki>http://host/path</nowiki>}} access scheme or {{mono|<nowiki>https://host/path</nowiki>}} for secure connections using ssl.
# Custom "svn" protocol (default [[List of TCP and UDP port numbers|port]] 3690), using plain text or over [[TCP/IP]]. This mode uses either the {{mono|<nowiki>svn://host/path</nowiki>}} access scheme for unencrypted transport or {{mono|<nowiki>svn+ssh://host/path</nowiki>}} scheme for tunneling over ssh.

All three means can access both FSFS and Berkeley DB repositories.

Any 1.x version of a client can work with any 1.x server. Newer clients and servers have additional features and performance capabilities, but have fallback support for older clients/servers.<ref>[https://subversion.apache.org/docs/release-notes/1.5.html SVN 1.5 release notes]</ref>

==Layers==
Internally, a Subversion system comprises several libraries arranged as layers. Each performs a specific task and allows developers to create their own tools at the desired level of complexity and specificity.

; Fs : The lowest level; it implements the versioned filesystem which stores the user data.
; Repos : Concerned with the repository built up around the filesystem. It has many helper functions and handles the various "hooks" that a repository may have, e.g., scripts that run when an action is performed. Together, Fs and Repos constitute the "filesystem interface".
; mod_dav_svn : Provides [[WebDAV]]/Delta-V access through Apache 2.
; Ra : Handles "repository access", both local and remote. From this point on, repositories are referred to using URLs, e.g.
:* {{mono|file:///path/}} for local access,
:* {{mono|<nowiki>http://host/path/</nowiki>}} or {{mono|<nowiki>https://host/path/</nowiki>}} for WebDAV access, or
:* {{mono|<nowiki>svn://host/path/</nowiki>}} or {{mono|<nowiki>svn+ssh://host/path/</nowiki>}} for the SVN protocol.
; Client, Wc : The highest level. It abstracts repository access and provides common client tasks, such as authenticating users or comparing versions. Subversion clients use the Wc library to manage the local working copy.

==Filesystem==
[[File:Svn 3D-tree.svg|right|thumb]]
One can view the Subversion filesystem as "two-dimensional".<ref>[https://svnbook.red-bean.com/nightly/en/svn.branchmerge.basicmerging.html#svn.branchmerge.basicmerging.resurrect Basic Merging<!-- Bot generated title -->]</ref> Two coordinates are used to unambiguously address filesystem items:
* '''Path''' (regular [[Path (computing)|path]] of [[Unix-like]] OS filesystem)
* '''Revision'''
Each revision in a Subversion filesystem has its own ''[[root directory|root]]'', which is used to access contents at that revision. Files are stored as links to the most recent change; thus a Subversion repository is quite compact. The system consumes storage space proportional to the number of changes made, not to the number of revisions.

The Subversion filesystem uses transactions to keep changes [[Atomicity (database systems)|atomic]]. A transaction operates on a specified revision of the filesystem, not necessarily the latest. The transaction has its own ''root'', on which changes are made. It is then either committed and becomes the latest revision, or is aborted. The transaction is actually a long-lived filesystem object; a client does not need to commit or abort a transaction itself, rather it can also begin a transaction, exit, and then can re-open the transaction and continue using it. Potentially, multiple clients can access the same transaction and work together on an atomic change, though no existing clients expose this capability.

==Properties==
One important feature of the Subversion filesystem is properties: simple ''name''=''value'' pairs of text. Most properties occur on filesystem entries (i.e., files and directories). These are versioned just like other changes to the filesystem. The Subversion client reserves the 'svn:' prefix for built-in properties, but other names can be used to define custom properties.

; {{mono|svn:executable}} : Makes a file on [[Unix]]-hosted working copies executable, when supported by the filesystem.
; {{mono|svn:mime-type}} : Stores the [[Internet media type]] ("MIME type") of a file. Affects the handling of diffs and merging.
; {{mono|svn:ignore}} : A list of filename patterns to ignore in a directory. Similar to [[Concurrent Versions System|CVS]]'s <code>.cvsignore</code> file.
; {{mono|svn:keywords}} : A list of ''keywords'' to substitute into a file when changes are made. The file itself must also reference the keywords as {{mono|$keyword$}} or {{mono|$keyword:...$}}. This is used to maintain certain information (e.g., author, date of last change, revision number) in a file without human intervention.<br />The keyword substitution mechanism originates from [[Revision Control System|RCS]] and from CVS.<ref>{{cite web|url=https://man.openbsd.org/OpenBSD-current/man1/rcs.1|title=rcs(1)|work=OpenBSD manual pages}}</ref>
; {{mono|svn:eol-style}} : Makes the client convert [[Newline|end-of-line]] characters in text files. Used when the working copy is needed with a specific EOL style. "native" is commonly used, so that EOLs match the user's OS EOL style. Repositories may require this property on all files to prevent inconsistent line endings, which can cause a problem in itself.
; {{mono|svn:externals}} : Allows parts of other repositories to be automatically checked out into a subdirectory.
; {{mono|svn:needs-lock}} : Specifies that a file is to be checked out with file permissions set to read-only. This is designed for use with the locking mechanism. The read-only permission reminds one to obtain a lock before modifying the file: obtaining a lock makes the file writable, and releasing the lock makes it read-only again. Locks are only enforced during a commit operation. Locks can be used without setting this property. However, that is not recommended, because it introduces the risk of someone modifying a locked file; they will only discover it has been locked when their commit fails.
; {{mono|svn:special}} : This property is not meant to be set or modified directly by users. {{As of | 2010}} it is only used for having [[symbolic link]]s in the repository. When a symbolic link is added to the repository, a file containing the link target is created with this property set. When a Unix-like system checks out this file, the client converts it to a symbolic link.
; {{mono|svn:mergeinfo}} : Used to track merge data (revision numbers) in Subversion 1.5 (or later). This property is automatically maintained by the {{mono|merge}} command, and it is not recommended to change its value manually.<ref>[https://svnbook.red-bean.com/en/1.5/svn.ref.properties.html Subversion Properties<!-- Bot generated title -->]</ref>

Subversion also uses properties on revisions themselves. Like the above properties on filesystem entries, the names are completely arbitrary, with the Subversion client using certain properties prefixed with 'svn:'. However, these properties are not versioned, and they can be changed later if allowed by a pre-revprop-change hook.<ref>[https://svnbook.red-bean.com/en/1.7/svn.ref.reposhooks.pre-revprop-change.html pre-revprop-change]</ref>

; {{mono|svn:date}} : The date and time stamp of a revision.
; {{mono|svn:author}} : The name of the user that submitted the change(s).
; {{mono|svn:log}} : The user-supplied description of the change(s).

==Branching and tagging==
Subversion uses the inter-file branching model from [[Perforce]]<ref>[http://www.perforce.com/perforce/branch.html Inter-File Branching: A Practical Method for Representing Variants] {{webarchive|url=https://web.archive.org/web/20070714160428/http://www.perforce.com/perforce/branch.html |date=2007-07-14 }}</ref> to implement [[Branching (software)|branches]] and [[Revision tag|tagging]]. A branch is a separate line of development.<ref>[https://tortoisesvn.net/docs/release/TortoiseSVN_en/tsvn-dug-branchtag.html Branching / Tagging — TortoiseSVN]</ref> Tagging refers to labeling the repository at a certain point in time so that it can be easily found in the future. In Subversion, the only difference between branches and tags is how they are used.

A new branch or tag is set up by using the "{{mono|svn copy}}" command, which should be used in place of the native operating system mechanism. The copied directory is linked to the original in the repository to preserve its history, and the copy takes very little extra space in the repository.

All the versions in each branch maintain the history of the file up to the point of the copy, plus any changes made since. One can "merge" changes back into the [[Trunk (software)|trunk]] or between branches.

{{Wide image|Subversion project visualization.svg|815|Visualization of a simple Subversion project|100%|center|alt=alt text}}

==Limitations and problems==
A known problem in Subversion affects the implementation of the file and directory rename operation. {{As of|2014}}, Subversion implements the renaming of files and directories as a "copy" to the new name followed by a "delete" of the old name. Only the names change, all data relating to the edit history remains the same, and Subversion will still use the old name in older revisions of the "tree". However, Subversion may become confused when a move conflicts with edits made elsewhere,<ref>{{Cite web |url=http://subversion.tigris.org/issues/show_bug.cgi?id=898 |title=Implement true renames |access-date=2007-05-11 |archive-date=2002-12-01 |archive-url=https://web.archive.org/web/20021201064344/http://subversion.tigris.org/issues/show_bug.cgi?id=898 |url-status=dead }}</ref> both for regular commits and when merging branches.<ref>[https://svnbook.red-bean.com/en/1.7/svn.branchmerge.advanced.html#svn.branchmerge.advanced.moves Advanced Merging]</ref> The Subversion 1.5 release addressed some of these scenarios while others remained problematic.<ref>[https://subversion.apache.org/docs/release-notes/1.5.html#copy-move-improvements Copy/move-related improvements in Subversion 1.5]</ref> The Subversion 1.8 release addressed some of these problems by making moves a first-class operation on the client, but it is still treated as copy+delete in the repository.<ref>[https://subversion.apache.org/docs/release-notes/1.8.html#moves Working copy records moves as first-class operation in Subversion 1.8]</ref>

{{As of | 2013}}, Subversion lacks some repository-administration and management features. For instance, someone may wish to edit the repository to permanently remove all historical records of certain data. Subversion does not have built-in support to achieve this simply.<ref>{{Cite web |url=https://issues.apache.org/jira/browse/SVN-516 |title=[SVN-516] svn obliterate |access-date=2023-09-04 }}</ref>

Subversion stores additional copies of data on the local machine, which can become an issue with very large projects or files, or if developers work on multiple branches simultaneously. In versions prior to 1.7 these <code>.svn</code> directories on the client side could become corrupted by ill-advised user activity like global search/replace operations.<ref>{{Cite web|url=https://stackoverflow.com/a/579442|title=Subclipse - Repair SVN Checksum}}</ref> Starting with version 1.7 Subversion uses a single centralized {{mono|.svn}} folder per working area.<ref>[https://subversion.apache.org/docs/release-notes/1.7.html#wc-ng Working Copy Metadata Storage Improvements (client)]</ref>

Subversion does not store the modification times of files. As such, a file checked out of a Subversion repository will have the 'current' date (instead of the modification time in the repository), and a file checked into the repository will have the date of the check-in (instead of the modification time of the file being checked in). This might not always be what is wanted.<ref>{{Cite web |url=https://issues.apache.org/jira/browse/SVN-1256 |title=[SVN-1256] Ability to preserve last modification time (mtime) of files under version control |access-date=2023-09-04 }}</ref>
To mitigate this, third-party tools exist that allow for preserving modification time and other filesystem meta-data.<ref>[https://sourceforge.net/projects/freezeattrib/files/ FreezeAttrib (saves/restores file attributes using properties)]</ref><ref>{{GitHub|phmarek/fsvs|fsvs – Full System Versioning System}}<!-- previously "FSVS (Fast System VerSioning)" archived at https://web.archive.org/web/20100825094540/http://fsvs.tigris.org/ --></ref>
However, giving checked out files a current date is important as well — this is how tools like [[make (software)|make(1)]] will take notice of a changed file for rebuilding it.

Subversion uses a centralized [[revision control]] model. [[Ben Collins-Sussman]], one of the designers of Subversion, believes a centralised model would help prevent "insecure programmers" from hiding their work from other team members during development.<ref>[http://blog.red-bean.com/sussman/?p=96 Programmer Insecurity @ iBanjo<!-- Bot generated title -->]</ref> Some users of version control systems see the centralised model as detrimental; famously, [[Linus Torvalds]] attacked Subversion's model and its developers.<ref>[https://www.youtube.com/watch?v=4XpnKHJAok8 Google Tech Talk video] and its [https://web.archive.org/web/20110725034129/https://git.wiki.kernel.org/index.php/LinusTalk200705Transcript transcript]</ref>

Subversion often does not deal well with the [[Unicode equivalence#Normalization|filename normalization]] performed by the [[HFS+]] filesystem. This can cause problems when files with accented characters in their names are added to the repository on a non-HFS+ filesystem and the repository is then used with HFS+.<ref>{{Cite web |url=https://issues.apache.org/jira/browse/SVN-2464 |title=[SVN-2464] Canonicalize / stringprep UTF-8 filenames to handle composed / decomposed differences shown by e.g. Mac OS X HFS+ |access-date=2023-09-04 }}</ref>

===Subversion tags and branches===
Revision numbers are difficult to remember in any version-control system. For this reason, most systems offer symbolic ''tags'' as user-friendly references to them. Subversion does not have such a feature and what its documentation recommends to use instead is very different in nature. Instead of implementing tags as ''references'' to points in history, Subversion recommends making snapshot ''copies'' into a well-known subdirectory ("{{code|tags/}}") in the space of the repository tree. Only a few predefined ''references'' are available: {{code|HEAD}}, {{code|BASE}}, {{code|PREV}} and {{code|COMMITTED}}.

This history-to-space projection has multiple issues:

{{ordered list
| When a snapshot is taken, the system does not assign any special meaning to the name of the tag/snapshot. This is the difference between a ''copy'' and a ''reference''. The revision is recorded and the snapshot can be accessed by URL. This makes some operations less convenient and others impossible. For instance, a naive {{code|svn diff -r tag1:tag2 myfile}} does not work; it is slightly more complicated than that to achieve, requiring the user to know and input URL/paths to the snapshots instead of just the names: {{code|svn diff <URL-TO-TAG1>/myfile <URL-TO-TAG2>/myfile}}. Other operations like for instance {{code|svn log -r tag1:tag2 myfile}} are just impossible.

| When two (ideally independent) object types live in the repository tree, a "fight to the top" can ensue. In other words, it is often difficult to decide at which level to create the {{code|tags/}} subdirectory:

{{(!}}
{{!}}
 '''trunk'''/
      /component'''foo'''/
      /component'''bar'''/
 '''tags'''/
     /1.1/
         /component'''foo'''/
         /component'''bar'''/
{{!}} &nbsp;or&nbsp;
{{!}}
 component'''foo'''/
             /'''trunk'''/
             /'''tags'''/
                  /1.1/
 component'''bar'''/
             /'''trunk'''/
             /'''tags'''/
                  /1.1/
{{!)}}

| Tags, by their conventional definition, are both read-only and light-weight, on the repository and client. Subversion copies are not read-only, and while they are light-weight on the repository, they are incredibly heavy-weight on the client.}}

To address such issues, posters on the Subversion mailing lists have suggested a new feature called "labels" or "aliases".<ref>For example: {{cite mailing list |url=https://svn.haxx.se/dev/archive-2005-05/1095.shtml |title=Subversion 'labels' vs. 'tags' |date=23 May 2005 |access-date=5 May 2020 |mailing-list=SVN Dev |last=Weintraub |first=David }}</ref> SVN labels would more closely resemble the "tags" of other systems such as [[Concurrent Versions System|CVS]] or [[Git (software)|Git]]. The fact that Subversion has global revision numbers opens the way to a very simple label → revision implementation. Yet as of 2013, no progress has been made and symbolic tags are not in the list of the most wanted features.<ref>{{cite web |url=https://subversion.apache.org/roadmap.html |title=Apache Subversion Roadmap |publisher=Apache Project |access-date=5 May 2020}}</ref>

==Development and implementation==
[[CollabNet]] has continued its involvement with Subversion, but the project runs as an independent open source community. In November 2009, the project was accepted into the Apache Incubator, aiming to become part of the [[Apache Software Foundation]]'s efforts.<ref>{{Cite web |title=Subversion Submitted to Become a Project at The Apache Software Foundation |url=https://apache.org/foundation/press/pr_2009_11_04.html |date=November 4, 2009 |access-date=October 1, 2019}}</ref> Since March 2010, the project is formally known as Apache Subversion, being a part of the Apache Top-Level Projects.<ref name=CollabNetPR2010>{{cite web|title=CollabNet Supports Subversion's Graduation to Apache Top-Level Project|url=http://www.open.collab.net/news/press/2010/apache.html|publisher=CollabNet|archive-url=https://web.archive.org/web/20100311192650/http://www.open.collab.net/news/press/2010/apache.html|archive-date=2010-03-11|date=1 March 2010}}</ref>

In October 2009, [[WANdisco]] announced the hiring of core Subversion committers as the company moved to become a major corporate sponsor of the project. This included Hyrum Wright, president of the Subversion Corporation and release manager for the Subversion project since early 2008, who joined the company to lead its open source team.<ref>{{Cite news |title= WANdisco Names Hyrum Wright to Lead Subversion Open Source Efforts |date= January 7, 2010 |work= News release |author= WANdisco |publisher= Open Source magazine |url= http://opensource.sys-con.com/node/1239202 |access-date= October 29, 2011 |archive-url=https://web.archive.org/web/20120118161238/http://opensource.sys-con.com/node/1239202 |archive-date=2012-01-18 |url-status=live}}</ref>

The Subversion open-source community does not provide binaries, but potential users can download binaries from volunteers.<ref>{{Cite web |title= Apache Subversion Binary Packages |work= Official project website |url= https://subversion.apache.org/packages.html |access-date= October 29, 2011 }}</ref> While the Subversion project does not include an official [[graphical user interface]] (GUI) for use with Subversion, third parties have developed a number of different GUIs, along with a wide variety of additional ancillary software.

Work announced in 2009 included SubversionJ (a [[Java API]]) and implementation of the Obliterate command, similar to that provided by [[Perforce]]. Both of these enhancements were sponsored by WANdisco.<ref>{{Cite news|title=WANdisco Presents New Initiatives for the Subversion Open Source Project |author=WANdisco |publisher=CM Crossroads |work=News release |date=October 28, 2009 |url=http://www.cmcrossroads.com/index.php?Itemid=100152&catid=101:news-and-announcements&id=13065:wandisco-presents-new-initiatives-for-the-subversion-open-source-project-&option=com_content&view=article |access-date=October 29, 2011 |archive-url=https://web.archive.org/web/20111118040455/http://www.cmcrossroads.com/index.php?Itemid=100152&catid=101%3Anews-and-announcements&id=13065%3Awandisco-presents-new-initiatives-for-the-subversion-open-source-project-&option=com_content&view=article |archive-date=2011-11-18 |url-status=dead }}</ref>

The Subversion committers normally have at least one or two new features under active development at any one time. The 1.7 release of Subversion in October 2011 included a streamlined HTTP transport to improve performance and a rewritten working-copy library.<ref>{{Cite web |title= Apache Subversion Roadmap |work= Official project website |url= https://subversion.apache.org/roadmap.html |access-date= October 29, 2011 }}</ref>

In 2002, [http://svn.apache.org/repos/asf/subversion/svn-logos/README.html a design contest] was held to select the logo for Subversion. The original entries can be found [http://svn.apache.org/repos/asf/subversion/svn-logos/entries.html here] as well as the [http://svn.apache.org/repos/asf/subversion/svn-logos/VOTES votes] for each logo. The current logo received the most votes in the contest.

==See also==
{{Portal|Free and open-source software}}

* [[List of version-control software]]
* [[Comparison of version-control software]]
* [[Comparison of Subversion clients]]
* [[List of software that uses Subversion]]
* [[TortoiseSVN]]

==Notes==
{{notelist}}

==References==
===Footnotes===
{{Reflist}}

===Sources===
{{refbegin}}
* C. Michael Pilato, Ben Collins-Sussman, Brian W. Fitzpatrick; ''Version Control with Subversion''; O'Reilly; {{ISBN|0-596-00448-6}} (1st edition, paperback, 2004, [https://svnbook.red-bean.com/ full book online], [https://web.archive.org/web/20080107072118/http://www.mentalpointer.com/Subversion/svn-book.html mirror])
* Garrett Rooney; ''Practical Subversion''; Apress; {{ISBN|1-59059-290-5}} (1st edition, paperback, 2005)
* Mike Mason; ''Pragmatic Version Control Using Subversion''; Pragmatic Bookshelf; {{ISBN|0-9745140-6-3}} (1st edition, paperback, 2005)
* William Nagel; ''Subversion Version Control: Using the Subversion Version Control System in Development Projects''; Prentice Hall; {{ISBN|0-13-185518-2}} (1st edition, paperback, 2005)
{{refend}}

==Further reading==
* [http://www.red-bean.com/sussman/svn-anti-fud.html Dispelling Subversion FUD] by Ben Collins-Sussman (Subversion developer), link broken as of 2013-03-07 (Internet Archive.org [[Wayback Machine]] [https://web.archive.org/web/20110718233416/http://www.red-bean.com/sussman/svn-anti-fud.html 2011-07-18 captured version], "last updated" 2004-12-21)

==External links==
* {{Official website}}

{{Version control software}}
{{Apache Software Foundation}}
{{Authority control}}

[[Category:Apache Software Foundation projects|Subversion]]
[[Category:Collaborative software]]
[[Category:Concurrent Versions System]]
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[[Category:Free version control software]]
[[Category:Software using the Apache license]]
[[Category:Apache Subversion| ]]
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