<s>
GNU	B-Protocol
arch	I-Protocol
software	O
is	O
a	O
distributed	B-Protocol
revision	I-Protocol
control	I-Protocol
system	I-Protocol
that	O
is	O
part	O
of	O
the	B-Application
GNU	I-Application
Project	I-Application
and	O
licensed	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
As	O
of	O
2009	O
,	O
GNU	B-Protocol
arch	I-Protocol
's	O
official	O
status	O
is	O
deprecation	O
,	O
and	O
only	O
security	O
fixes	O
are	O
applied	O
.	O
</s>
<s>
Bazaar	B-Protocol
(	O
or	O
'	O
bzr	B-Protocol
 '	O
)	O
has	O
since	O
also	O
been	O
made	O
an	O
official	O
GNU	B-Application
project	I-Application
and	O
can	O
thus	O
be	O
considered	O
the	O
replacement	O
for	O
GNU	B-Protocol
arch	I-Protocol
.	O
</s>
<s>
It	O
is	O
not	O
a	O
fork	B-Application
of	O
arch	O
.	O
</s>
<s>
Being	O
a	O
distributed	B-Architecture
,	O
decentralized	O
versioning	B-Architecture
system	I-Architecture
,	O
each	O
revision	O
stored	O
using	O
arch	O
is	O
uniquely	O
globally	O
identifiable	O
;	O
such	O
identifier	O
can	O
be	O
used	O
in	O
a	O
distributed	B-Architecture
setting	O
to	O
easily	O
merge	O
or	O
"	O
cherry-pick	O
"	O
changes	O
from	O
completely	O
disparate	O
sources	O
.	O
</s>
<s>
As	O
with	O
other	O
systems	O
,	O
a	O
full	O
read-only	O
copy	O
of	O
a	O
project	O
is	O
made	O
accessible	O
in	O
an	O
"	O
official	O
"	O
repository	O
via	O
HTTP	B-Protocol
,	O
FTP	B-Protocol
,	O
or	O
SFTP	B-Protocol
;	O
but	O
then	O
,	O
contributors	O
are	O
encouraged	O
to	O
make	O
modifications	O
and	O
publish	O
them	O
in	O
a	O
public	O
archive	O
(	O
repository	O
)	O
of	O
their	O
own	O
,	O
so	O
that	O
the	O
head	O
developer	O
may	O
manually	O
merge	O
changesets	O
into	O
the	O
official	O
repository	O
.	O
</s>
<s>
To	O
simulate	O
the	O
behavior	O
of	O
centralized	O
revision	B-Architecture
control	I-Architecture
systems	I-Architecture
,	O
the	O
head	O
developer	O
could	O
allow	O
shell	B-Operating_System
access	I-Operating_System
(	O
SSH	B-Protocol
)	O
or	O
write	O
access	O
(	O
FTP	B-Protocol
,	O
SFTP	B-Protocol
,	O
WebDAV	B-Protocol
)	O
to	O
a	O
server	O
,	O
allowing	O
authorized	O
users	O
to	O
commit	O
to	O
a	O
central	O
server	O
.	O
</s>
<s>
GNU	B-Protocol
arch	I-Protocol
has	O
several	O
other	O
features	O
:	O
</s>
<s>
Atomic	B-Operating_System
commits	I-Operating_System
Commits	O
are	O
all-or-nothing	O
.	O
</s>
<s>
Changeset	O
oriented	O
Instead	O
of	O
tracking	O
individual	O
files	O
(	O
as	O
in	O
CVS	B-Application
)	O
,	O
GNU	B-Protocol
arch	I-Protocol
tracks	O
changesets	O
,	O
which	O
are	O
akin	O
to	O
patches	O
.	O
</s>
<s>
Cryptographic	O
signatures	O
Every	O
changeset	O
is	O
stored	O
with	O
a	O
hash	B-Algorithm
to	O
prevent	O
accidental	O
corruption	O
.	O
</s>
<s>
Using	O
an	O
external	O
file	O
signing	O
program	O
(	O
such	O
as	O
GnuPG	B-Application
or	O
another	O
PGP	B-Application
client	O
)	O
,	O
these	O
hashes	B-Algorithm
can	O
also	O
optionally	O
be	O
signed	O
,	O
preventing	O
unauthorized	O
modification	O
if	O
the	O
archive	O
is	O
compromised	O
.	O
</s>
<s>
Symbolic	B-Application
links	I-Application
are	O
supported	O
and	O
are	O
tracked	O
the	O
same	O
way	O
as	O
files	O
and	O
directories	O
.	O
</s>
<s>
The	O
original	O
author	O
and	O
maintainer	B-General_Concept
of	O
GNU	B-Protocol
arch	I-Protocol
was	O
Thomas	O
Lord	O
who	O
started	O
the	O
project	O
in	O
2001	O
.	O
</s>
<s>
The	O
command	O
used	O
to	O
manipulate	O
GNU	B-Protocol
arch	I-Protocol
repositories	O
is	O
tla	O
,	O
an	O
initialism	O
for	O
Tom	B-Protocol
Lord	I-Protocol
's	I-Protocol
Arch	I-Protocol
.	O
</s>
<s>
Lord	O
started	O
GNU	B-Protocol
arch	I-Protocol
as	O
a	O
collection	O
of	O
shell	B-Language
scripts	I-Language
to	O
provide	O
an	O
alternative	O
to	O
CVS	B-Application
.	O
</s>
<s>
In	O
2003	O
,	O
arch	O
became	O
part	O
of	O
the	B-Application
GNU	I-Application
project	I-Application
.	O
</s>
<s>
The	O
GNU	B-Protocol
arch	I-Protocol
project	O
forked	O
several	O
times	O
,	O
resulting	O
in	O
both	O
Canonical	O
Ltd.	O
'	O
s	O
now	O
abandoned	O
Baz	O
fork	B-Application
and	O
Walter	O
Landry	O
's	O
ArX	B-Application
project	O
.	O
</s>
<s>
Both	O
forks	B-Application
provoked	O
a	O
hostile	O
reaction	O
:	O
the	O
ArX	B-Application
fork	B-Application
was	O
due	O
to	O
a	O
serious	O
dispute	O
in	O
direction	O
and	O
Lord	O
was	O
strongly	O
critical	O
of	O
Canonical	O
's	O
approach	O
to	O
announcing	O
the	O
Baz	O
project	O
.	O
</s>
<s>
In	O
August	O
2005	O
Lord	O
announced	O
that	O
he	O
was	O
resigning	O
as	O
the	O
maintainer	B-General_Concept
of	O
GNU	B-Protocol
arch	I-Protocol
and	O
recommended	O
that	O
Baz	O
become	O
the	O
main	O
GNU	B-Protocol
arch	I-Protocol
project	O
.	O
</s>
<s>
However	O
,	O
this	O
did	O
not	O
happen	O
:	O
the	O
Baz	O
fork	B-Application
was	O
abandoned	O
by	O
Canonical	O
in	O
favour	O
of	O
the	O
separate	O
Bazaar	B-Protocol
project	O
,	O
with	O
the	O
1.5	O
release	O
of	O
Baz	O
being	O
scrapped	O
in	O
2006	O
.	O
</s>
<s>
In	O
October	O
,	O
2005	O
,	O
Andy	O
Tai	O
announced	O
that	O
Lord	O
and	O
the	B-Operating_System
Free	I-Operating_System
Software	I-Operating_System
Foundation	I-Operating_System
had	O
accepted	O
his	O
offer	O
to	O
be	O
the	O
maintainer	B-General_Concept
of	O
GNU	B-Protocol
arch	I-Protocol
.	O
</s>
<s>
Tai	O
subsequently	O
merged	O
many	O
features	O
from	O
Baz	O
back	O
into	O
tla	O
,	O
but	O
in	O
March	O
2008	O
indicated	O
that	O
tla	O
was	O
no	O
longer	O
under	O
active	O
development	O
and	O
was	O
no	O
longer	O
competitive	O
with	O
other	O
version	B-Architecture
control	I-Architecture
systems	I-Architecture
.	O
</s>
<s>
revc	O
was	O
a	O
prototype	O
revision	B-Architecture
control	I-Architecture
project	O
by	O
Thomas	O
Lord	O
that	O
he	O
intended	O
to	O
become	O
GNU	B-Protocol
arch	I-Protocol
2.0	O
,	O
designed	O
to	O
be	O
a	O
radical	O
departure	O
from	O
tla	O
and	O
to	O
draw	O
many	O
ideas	O
from	O
the	O
Git	B-Application
revision	B-Architecture
control	I-Architecture
system	I-Architecture
.	O
</s>
<s>
It	O
was	O
announced	O
in	O
June	O
2005	O
,	O
the	O
first	O
pre-release	O
was	O
in	O
July	O
and	O
the	O
last	O
in	O
August	O
,	O
just	O
prior	O
to	O
Lord	O
's	O
resignation	O
as	O
maintainer	B-General_Concept
.	O
</s>
<s>
As	O
of	O
2008	O
the	O
last	O
pre-release	O
,	O
0.0x2	O
,	O
of	O
revc	O
is	O
still	O
available	O
and	O
Lord	O
is	O
still	O
interested	O
in	O
some	O
of	O
the	O
ideas	O
in	O
GNU	B-Protocol
arch	I-Protocol
but	O
does	O
not	O
have	O
the	O
resources	O
to	O
resume	O
development	O
of	O
revc	O
.	O
</s>
<s>
Perhaps	O
the	O
most	O
common	O
criticism	O
of	O
GNU	B-Protocol
arch	I-Protocol
is	O
that	O
it	O
is	O
difficult	O
to	O
learn	O
,	O
even	O
for	O
users	O
who	O
have	O
experience	O
with	O
other	O
SCM	O
systems	O
.	O
</s>
<s>
In	O
particular	O
,	O
GNU	B-Protocol
arch	I-Protocol
has	O
a	O
large	O
number	O
of	O
commands	O
,	O
which	O
can	O
be	O
intimidating	O
for	O
new	O
users	O
and	O
some	O
design	O
elements	O
arguably	O
too	O
strongly	O
enforce	O
Lord	O
's	O
taste	O
in	O
version	B-Architecture
control	I-Architecture
practices	O
.	O
</s>
<s>
Some	O
also	O
criticize	O
GNU	B-Protocol
arch	I-Protocol
for	O
using	O
very	O
unusual	O
file	O
naming	O
conventions	O
(	O
)	O
,	O
which	O
can	O
create	O
difficulties	O
for	O
using	O
it	O
in	O
scripts	O
,	O
some	O
shells	O
,	O
and	O
in	O
porting	O
it	O
to	O
non-Unix	O
operating	O
systems	O
.	O
</s>
<s>
GNU	B-Protocol
arch	I-Protocol
has	O
been	O
criticised	O
for	O
having	O
a	O
slow	O
running	O
time	O
as	O
part	O
of	O
a	O
design	O
decision	O
to	O
lessen	O
internal	O
code	O
complexity	O
.	O
</s>
