<s>
Apache	B-Application
Subversion	O
(	O
often	O
abbreviated	O
SVN	O
,	O
after	O
its	O
command	O
name	O
svn	O
)	O
is	O
a	O
software	O
versioning	O
and	O
revision	B-Architecture
control	I-Architecture
system	I-Architecture
distributed	O
as	O
open	B-Application
source	I-Application
under	O
the	O
Apache	B-Application
License	I-Application
.	O
</s>
<s>
Its	O
goal	O
is	O
to	O
be	O
a	O
mostly	O
compatible	O
successor	O
to	O
the	O
widely	O
used	O
Concurrent	B-Application
Versions	I-Application
System	I-Application
(	O
CVS	B-Application
)	O
.	O
</s>
<s>
The	O
open	B-Application
source	I-Application
community	O
has	O
used	O
Subversion	O
widely	O
:	O
for	O
example	O
,	O
in	O
projects	O
such	O
as	O
Apache	B-Application
Software	O
Foundation	O
,	O
Free	B-Operating_System
Pascal	I-Operating_System
,	O
FreeBSD	B-Operating_System
,	O
SourceForge	B-Application
,	O
and	O
from	O
2006	O
to	O
2019	O
,	O
GCC	B-Application
.	O
</s>
<s>
CodePlex	B-Protocol
was	O
previously	O
a	O
common	O
host	O
for	O
Subversion	O
repositories	O
.	O
</s>
<s>
Subversion	O
was	O
created	O
by	O
CollabNet	O
Inc	O
.	O
in	O
2000	O
,	O
and	O
is	O
now	O
a	O
top-level	O
Apache	B-Application
project	O
being	O
built	O
and	O
used	O
by	O
a	O
global	O
community	O
of	O
contributors	O
.	O
</s>
<s>
CollabNet	O
founded	O
the	O
Subversion	O
project	O
in	O
2000	O
as	O
an	O
effort	O
to	O
write	O
an	O
open-source	B-Application
version-control	B-Architecture
system	O
which	O
operated	O
much	O
like	O
CVS	B-Application
but	O
which	O
fixed	O
the	O
bugs	O
and	O
supplied	O
some	O
features	O
missing	O
in	O
CVS	B-Application
.	O
</s>
<s>
In	O
November	O
2009	O
,	O
Subversion	O
was	O
accepted	O
into	O
Apache	B-Application
Incubator	I-Application
:	O
this	O
marked	O
the	O
beginning	O
of	O
the	O
process	B-Operating_System
to	O
become	O
a	O
standard	O
top-level	O
Apache	B-Application
project	O
.	O
</s>
<s>
It	O
became	O
a	O
top-level	O
Apache	B-Application
project	O
on	O
February	O
17	O
,	O
2010	O
.	O
</s>
<s>
Release	O
dates	O
are	O
extracted	O
from	O
Apache	B-Application
Subversion	O
's	O
file	O
,	O
which	O
records	O
all	O
release	O
history	O
.	O
</s>
<s>
Commits	B-Language
as	O
true	O
atomic	B-General_Concept
operations	I-General_Concept
(	O
interrupted	O
commit	O
operations	O
in	O
CVS	B-Application
would	O
cause	O
repository	O
inconsistency	O
or	O
corruption	O
)	O
.	O
</s>
<s>
Versioning	O
of	O
symbolic	B-Application
links	I-Application
.	O
</s>
<s>
Native	O
support	O
for	O
binary	O
files	O
,	O
with	O
space-efficient	O
binary-diff	O
storage	O
.	O
</s>
<s>
Apache	B-Application
HTTP	I-Application
Server	I-Application
as	O
network	O
server	O
,	O
WebDAV/Delta	O
-V	O
for	O
protocol	O
.	O
</s>
<s>
There	O
is	O
also	O
an	O
independent	O
server	O
process	B-Operating_System
called	O
svnserve	O
that	O
uses	O
a	O
custom	O
protocol	O
over	O
TCP/IP	B-Protocol
.	O
</s>
<s>
Branching	B-General_Concept
is	O
implemented	O
by	O
a	O
copy	O
of	O
a	O
directory	O
,	O
thus	O
it	O
is	O
a	O
cheap	O
operation	O
,	O
independent	O
of	O
file	O
size	O
.	O
</s>
<s>
Natively	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
,	O
layered	B-Architecture
library	B-Library
design	O
.	O
</s>
<s>
Client/server	B-Operating_System
protocol	I-Operating_System
sends	O
diffs	B-Application
in	O
both	O
directions	O
.	O
</s>
<s>
Parsable	B-Language
output	O
,	O
including	O
XML	B-Protocol
log	O
output	O
.	O
</s>
<s>
Open	B-Application
source	I-Application
licensed	O
–	O
Apache	B-Application
License	I-Application
since	O
the	O
1.7	O
release	O
;	O
prior	O
versions	O
use	O
a	O
derivative	O
of	O
the	O
Apache	B-Application
Software	I-Application
License	I-Application
1.1	O
.	O
</s>
<s>
Internationalized	B-General_Concept
program	O
messages	O
.	O
</s>
<s>
File	B-Application
locking	I-Application
for	O
unmergeable	O
files	O
(	O
"	O
reserved	O
checkouts	O
"	O
)	O
.	O
</s>
<s>
Path-based	O
authorization	O
.	O
</s>
<s>
Language	B-Application
bindings	I-Application
for	O
C#	B-Application
,	O
PHP	B-Application
,	O
Python	B-Language
,	O
Perl	B-Language
,	O
Ruby	B-Language
,	O
and	O
Java	B-Language
.	O
</s>
<s>
Full	O
MIME	B-Protocol
support	O
–	O
users	O
can	O
view	O
or	O
change	O
the	O
MIME	B-Application
type	I-Application
of	O
each	O
file	O
,	O
with	O
the	O
software	O
knowing	O
which	O
MIME	B-Application
types	I-Application
can	O
have	O
their	O
differences	O
from	O
previous	O
versions	O
shown	O
.	O
</s>
<s>
Merge	O
tracking	O
–	O
merges	O
between	O
branches	B-General_Concept
will	O
be	O
tracked	O
,	O
this	O
allows	O
automatic	O
merging	O
between	O
branches	B-General_Concept
without	O
telling	O
Subversion	O
what	O
does	O
and	O
does	O
not	O
need	O
to	O
be	O
merged	O
.	O
</s>
<s>
Changelists	O
to	O
organize	O
commits	B-Language
into	O
commit	O
groups	O
.	O
</s>
<s>
The	O
original	O
development	O
of	O
Subversion	O
used	O
the	O
Berkeley	B-Language
DB	I-Language
package	O
.	O
</s>
<s>
Subversion	O
has	O
some	O
limitations	O
with	O
Berkeley	B-Language
DB	I-Language
usage	O
when	O
a	O
program	O
that	O
accesses	O
the	O
database	O
crashes	O
or	O
terminates	O
forcibly	O
.	O
</s>
<s>
No	O
data	O
loss	O
or	O
corruption	O
occurs	O
,	O
but	O
the	O
repository	O
remains	O
offline	O
while	O
Berkeley	B-Language
DB	I-Language
replays	O
the	O
journal	O
and	O
cleans	O
up	O
any	O
outstanding	O
locks	O
.	O
</s>
<s>
The	O
safest	O
way	O
to	O
use	O
Subversion	O
with	O
a	O
Berkeley	B-Language
DB	I-Language
repository	O
involves	O
a	O
single	O
server-process	O
running	O
as	O
one	O
user	O
(	O
instead	O
of	O
through	O
a	O
shared	O
filesystem	O
)	O
.	O
</s>
<s>
The	O
Berkeley	B-Language
DB	I-Language
backend	O
was	O
deprecated	O
in	O
version	O
1.8	O
.	O
</s>
<s>
It	O
works	O
faster	O
than	O
the	O
Berkeley	B-Language
DB	I-Language
backend	O
on	O
directories	O
with	O
a	O
large	O
number	O
of	O
files	O
and	O
takes	O
less	O
disk	O
space	O
,	O
</s>
<s>
FSFS	O
stores	O
its	O
contents	O
directly	O
within	O
the	O
operating	O
system	O
's	O
filesystem	O
,	O
rather	O
than	O
a	O
structured	O
system	O
like	O
Berkeley	B-Language
DB	I-Language
.	O
</s>
<s>
WebDAV/Delta	O
-V	O
(	O
over	O
http	O
or	O
https	O
)	O
using	O
the	O
module	O
for	O
Apache	B-Application
2	I-Application
.	O
</s>
<s>
Custom	O
"	O
svn	O
"	O
protocol	O
(	O
default	O
port	B-Protocol
3690	O
)	O
,	O
using	O
plain	O
text	O
or	O
over	O
TCP/IP	B-Protocol
.	O
</s>
<s>
All	O
three	O
means	O
can	O
access	O
both	O
FSFS	O
and	O
Berkeley	B-Language
DB	I-Language
repositories	O
.	O
</s>
<s>
mod_dav_svn	O
Provides	O
WebDAV/Delta	O
-V	O
access	O
through	O
Apache	B-Application
2	I-Application
.	O
</s>
<s>
Subversion	B-Protocol
clients	I-Protocol
use	O
the	O
Wc	O
library	B-Library
to	O
manage	O
the	O
local	O
working	O
copy	O
.	O
</s>
<s>
Each	O
revision	O
in	O
a	O
Subversion	O
filesystem	O
has	O
its	O
own	O
root	B-Application
,	O
which	O
is	O
used	O
to	O
access	O
contents	O
at	O
that	O
revision	O
.	O
</s>
<s>
The	O
Subversion	O
filesystem	O
uses	O
transactions	O
to	O
keep	O
changes	O
atomic	B-General_Concept
.	O
</s>
<s>
The	O
transaction	O
has	O
its	O
own	O
root	B-Application
,	O
on	O
which	O
changes	O
are	O
made	O
.	O
</s>
<s>
Potentially	O
,	O
multiple	O
clients	O
can	O
access	O
the	O
same	O
transaction	O
and	O
work	O
together	O
on	O
an	O
atomic	B-General_Concept
change	O
,	O
though	O
no	O
existing	O
clients	O
expose	O
this	O
capability	O
.	O
</s>
<s>
Makes	O
a	O
file	O
on	O
Unix-hosted	O
working	O
copies	O
executable	O
,	O
when	O
supported	O
by	O
the	O
filesystem	O
.	O
</s>
<s>
Stores	O
the	O
Internet	B-Application
media	I-Application
type	I-Application
(	O
"	O
MIME	B-Application
type	I-Application
"	O
)	O
of	O
a	O
file	O
.	O
</s>
<s>
Affects	O
the	O
handling	O
of	O
diffs	B-Application
and	O
merging	O
.	O
</s>
<s>
Similar	O
to	O
CVS	B-Application
's	O
.cvsignore	O
file	O
.	O
</s>
<s>
This	O
is	O
used	O
to	O
maintain	O
certain	O
information	O
(	O
e.g.	O
,	O
author	O
,	O
date	O
of	O
last	O
change	O
,	O
revision	B-Architecture
number	I-Architecture
)	O
in	O
a	O
file	O
without	O
human	O
intervention.The	O
keyword	O
substitution	O
mechanism	O
originates	O
from	O
RCS	B-Architecture
and	O
from	O
CVS	B-Application
.	O
</s>
<s>
it	O
is	O
only	O
used	O
for	O
having	O
symbolic	B-Application
links	I-Application
in	O
the	O
repository	O
.	O
</s>
<s>
When	O
a	O
symbolic	B-Application
link	I-Application
is	O
added	O
to	O
the	O
repository	O
,	O
a	O
file	O
containing	O
the	O
link	O
target	O
is	O
created	O
with	O
this	O
property	O
set	O
.	O
</s>
<s>
When	O
a	O
Unix-like	B-Operating_System
system	I-Operating_System
checks	O
out	O
this	O
file	O
,	O
the	O
client	O
converts	O
it	O
to	O
a	O
symbolic	B-Application
link	I-Application
.	O
</s>
<s>
Used	O
to	O
track	O
merge	O
data	O
(	O
revision	B-Architecture
numbers	I-Architecture
)	O
in	O
Subversion	O
1.5	O
(	O
or	O
later	O
)	O
.	O
</s>
<s>
Subversion	O
uses	O
the	O
inter-file	O
branching	B-General_Concept
model	O
from	O
Perforce	B-General_Concept
to	O
implement	O
branches	B-General_Concept
and	O
tagging	B-Protocol
.	O
</s>
<s>
Tagging	B-Protocol
refers	O
to	O
labeling	O
the	O
repository	O
at	O
a	O
certain	O
point	O
in	O
time	O
so	O
that	O
it	O
can	O
be	O
easily	O
found	O
in	O
the	O
future	O
.	O
</s>
<s>
In	O
Subversion	O
,	O
the	O
only	O
difference	O
between	O
branches	B-General_Concept
and	O
tags	O
is	O
how	O
they	O
are	O
used	O
.	O
</s>
<s>
One	O
can	O
"	O
merge	O
"	O
changes	O
back	O
into	O
the	O
trunk	B-General_Concept
or	O
between	O
branches	B-General_Concept
.	O
</s>
<s>
However	O
,	O
Subversion	O
may	O
become	O
confused	O
when	O
a	O
move	O
conflicts	O
with	O
edits	O
made	O
elsewhere	O
,	O
both	O
for	O
regular	O
commits	B-Language
and	O
when	O
merging	O
branches	B-General_Concept
.	O
</s>
<s>
Subversion	O
stores	O
additional	O
copies	O
of	O
data	O
on	O
the	O
local	O
machine	O
,	O
which	O
can	O
become	O
an	O
issue	O
with	O
very	O
large	O
projects	O
or	O
files	O
,	O
or	O
if	O
developers	O
work	O
on	O
multiple	O
branches	B-General_Concept
simultaneously	O
.	O
</s>
<s>
Subversion	O
uses	O
a	O
centralized	O
revision	B-Architecture
control	I-Architecture
model	O
.	O
</s>
<s>
Some	O
users	O
of	O
version	B-Architecture
control	I-Architecture
systems	I-Architecture
see	O
the	O
centralised	O
model	O
as	O
detrimental	O
;	O
famously	O
,	O
Linus	O
Torvalds	O
attacked	O
Subversion	O
's	O
model	O
and	O
its	O
developers	O
.	O
</s>
<s>
Subversion	O
often	O
does	O
not	O
deal	O
well	O
with	O
the	O
filename	O
normalization	O
performed	O
by	O
the	O
HFS+	B-Application
filesystem	O
.	O
</s>
<s>
This	O
can	O
cause	O
problems	O
when	O
files	O
with	O
accented	O
characters	O
in	O
their	O
names	O
are	O
added	O
to	O
the	O
repository	O
on	O
a	O
non-HFS	O
+	O
filesystem	O
and	O
the	O
repository	O
is	O
then	O
used	O
with	O
HFS+	B-Application
.	O
</s>
<s>
Revision	B-Architecture
numbers	I-Architecture
are	O
difficult	O
to	O
remember	O
in	O
any	O
version-control	B-Architecture
system	O
.	O
</s>
<s>
SVN	O
labels	O
would	O
more	O
closely	O
resemble	O
the	O
"	O
tags	O
"	O
of	O
other	O
systems	O
such	O
as	O
CVS	B-Application
or	O
Git	B-Application
.	O
</s>
<s>
The	O
fact	O
that	O
Subversion	O
has	O
global	O
revision	B-Architecture
numbers	I-Architecture
opens	O
the	O
way	O
to	O
a	O
very	O
simple	O
label	O
→	O
revision	O
implementation	O
.	O
</s>
<s>
CollabNet	O
has	O
continued	O
its	O
involvement	O
with	O
Subversion	O
,	O
but	O
the	O
project	O
runs	O
as	O
an	O
independent	O
open	B-Application
source	I-Application
community	O
.	O
</s>
<s>
In	O
November	O
2009	O
,	O
the	O
project	O
was	O
accepted	O
into	O
the	O
Apache	B-Application
Incubator	I-Application
,	O
aiming	O
to	O
become	O
part	O
of	O
the	O
Apache	B-Application
Software	O
Foundation	O
's	O
efforts	O
.	O
</s>
<s>
Since	O
March	O
2010	O
,	O
the	O
project	O
is	O
formally	O
known	O
as	O
Apache	B-Application
Subversion	O
,	O
being	O
a	O
part	O
of	O
the	O
Apache	B-Application
Top-Level	O
Projects	O
.	O
</s>
<s>
In	O
October	O
2009	O
,	O
WANdisco	B-General_Concept
announced	O
the	O
hiring	O
of	O
core	O
Subversion	O
committers	O
as	O
the	O
company	O
moved	O
to	O
become	O
a	O
major	O
corporate	O
sponsor	O
of	O
the	O
project	O
.	O
</s>
<s>
This	O
included	O
Hyrum	O
Wright	O
,	O
president	O
of	O
the	O
Subversion	O
Corporation	O
and	O
release	O
manager	O
for	O
the	O
Subversion	O
project	O
since	O
early	O
2008	O
,	O
who	O
joined	O
the	O
company	O
to	O
lead	O
its	O
open	B-Application
source	I-Application
team	O
.	O
</s>
<s>
The	O
Subversion	O
open-source	B-Application
community	O
does	O
not	O
provide	O
binaries	O
,	O
but	O
potential	O
users	O
can	O
download	O
binaries	O
from	O
volunteers	O
.	O
</s>
<s>
While	O
the	O
Subversion	O
project	O
does	O
not	O
include	O
an	O
official	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
for	O
use	O
with	O
Subversion	O
,	O
third	O
parties	O
have	O
developed	O
a	O
number	O
of	O
different	O
GUIs	B-Application
,	O
along	O
with	O
a	O
wide	O
variety	O
of	O
additional	O
ancillary	O
software	O
.	O
</s>
<s>
Work	O
announced	O
in	O
2009	O
included	O
SubversionJ	O
(	O
a	O
Java	B-Language
API	I-Language
)	O
and	O
implementation	O
of	O
the	O
Obliterate	O
command	O
,	O
similar	O
to	O
that	O
provided	O
by	O
Perforce	B-General_Concept
.	O
</s>
<s>
Both	O
of	O
these	O
enhancements	O
were	O
sponsored	O
by	O
WANdisco	B-General_Concept
.	O
</s>
<s>
The	O
1.7	O
release	O
of	O
Subversion	O
in	O
October	O
2011	O
included	O
a	O
streamlined	O
HTTP	O
transport	O
to	O
improve	O
performance	O
and	O
a	O
rewritten	O
working-copy	O
library	B-Library
.	O
</s>
