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<!--
The FreeBSD Documentation Project
-->
<!DOCTYPE article PUBLIC "-//FreeBSD//DTD DocBook V4.1-Based Extension//EN" [
<!ENTITY % articles.ent PUBLIC "-//FreeBSD//ENTITIES DocBook FreeBSD Articles Entity Set//EN">
%articles.ent;
]>
<article>
<title>Perforce in &os; Development</title>
<articleinfo>
<authorgroup>
<author>
<firstname>Scott</firstname>
<surname>Long</surname>
<affiliation>
<address><email>scottl@FreeBSD.org</email>
</address>
</affiliation>
</author>
</authorgroup>
<pubdate>$FreeBSD$</pubdate>
<legalnotice id="trademarks" role="trademarks">
&tm-attrib.freebsd;
&tm-attrib.cvsup;
&tm-attrib.general;
</legalnotice>
</articleinfo>
<sect1 id="intro">
<title>Introduction</title>
<para>The &os; project uses the <application>Perforce</application>
version control system to manage experimental projects that are
not ready for the main CVS repository.</para>
<sect2 id="resources">
<title>Availability, Documentation, and Resources</title>
<para>While <application>Perforce</application> is a commercial
product, the client software for interacting with the server is
freely available from Perforce. Binary versions of the software
for most OS's, including &os;, are available for downloading
from the <application>Perforce</application> web site at <ulink
url="http://www.perforce.com/perforce/loadprog.html"></ulink>.</para>
<para>While there is a GUI client available, most people use the
command line application called <command>p4</command>. This
document is written from the point of view of using this
command.</para>
<para>Detailed documentation is available online at <ulink
url="http://www.perforce.com/perforce/technical.html"></ulink>.</para>
<para>Reading the <quote>Perforce User's Guide</quote> and
<quote>Perforce Command Reference</quote> is highly recommended.
The <application>p4</application> application also contains an
extensive amount of online help accessible via the <command>p4
help</command> command.</para>
<para>The &os; <application>Perforce</application> server is
hosted on <hostid role="fqdn">perforce.freebsd.org</hostid>,
port <literal>1666</literal>. The repository is browsable
online at <ulink url="http://perforce.freebsd.org"></ulink>.
Some portions of the repository are also automatically exported
to a number of <application>CVSup</application> servers.</para>
</sect2>
</sect1>
<sect1 id="start">
<title>Getting Started</title>
<para>The first step to using <application>Perforce</application> is
to obtain an account on the server. If you already have a <hostid
role="domainname">FreeBSD.org</hostid> account, log into <hostid
role="hostname">freefall</hostid>, run the following command, and
enter a password that is not the same as your &os; login or any
other SSH passphrase:</para>
<screen>&prompt.user; <userinput>/usr/local/bin/p4newuser</userinput></screen>
<para>Of course if you do not have a <hostid
role="domainname">FreeBSD.org</hostid> account, you will need to
coordinate with your sponsor.</para>
<para>The next step is to set the environment variables that
<command>p4</command> needs, and verify that it can connect to the
server. The <envar>P4PORT</envar> variable is required to be set
for all operations, and specifies the appropriate
<application>Perforce</application> server to talk to. For the
&os; project, set it like so:</para>
<screen>&prompt.user; <userinput>export P4PORT=perforce.freebsd.org:1666</userinput></screen>
<note>
<para>Users with shell access on the <hostid
role="domainname">FreeBSD.org</hostid> cluster may wish to tunnel
the <application>Perforce</application> client-server protocol via
an SSH tunnel, in which case the above string should be set to
<literal>localhost</literal>.</para>
</note>
<para>The &os; server also requires that the <envar>P4USER</envar>
and <envar>P4PASSWD</envar> variables be set. Use the username
and password from above, like so:</para>
<screen>&prompt.user; <userinput>export P4USER=<replaceable>username</replaceable></userinput>
&prompt.user; <userinput>export P4PASSWD=<replaceable>password</replaceable></userinput></screen>
<para>Test that this works by running the following command:</para>
<screen>&prompt.user; <userinput>p4 info</userinput></screen>
<para>This should return a list of information about the server. If
it does not, check that you have the <envar>P4PORT</envar>
variable set correctly.</para>
</sect1>
<sect1 id="clients">
<title>Clients</title>
<para><application>Perforce</application> provides access to the
repository and tracks state on a per-client basis. In
<application>Perforce</application> terms, a client is a
specification that maps files and directories from the repository
to the local machine. Each user can have multiple clients, and
each client can access different or overlapping parts of the
repository. The client also specifies the root directory of the
file tree that it maps, and it specifies the machine that the tree
lives on. Thus, working on multiple machines requires that
multiple clients be used.</para>
<para>Clients may be accessed via the <command>p4 client</command>
command. Running this command with no arguments will bring up a
client template in an editor, allowing you to create a new client
for your work. The important fields in this template are
explained below:</para>
<variablelist>
<varlistentry>
<term><literal>Client:</literal></term>
<listitem>
<para>This is the name of the client spec. It can be anything
you want, but it must be unique within the
<application>Perforce</application> server. A naming
convention that is commonly used is
<literal><replaceable>username</replaceable>_<replaceable>machinename</replaceable></literal>,
which makes it easy to identify clients when browsing them.
A default name will be filled in that is just the machine
name.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>Description:</literal></term>
<listitem>
<para>This can contain a simple text description to help
identify the client.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>Root:</literal></term>
<listitem>
<para>This is the local directory that will serve as the root
directory of all the files in the client mapping. This should
be a unique location in your filesystem that does not overlap
with other files or <application>Perforce</application>
clients.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>Options:</literal></term>
<listitem>
<para>Most of the default options are fine, though it is
usually a good idea to make sure that the
<option>compress</option> and <option>rmdir</option> options
are present and do not have a <literal>no</literal> prefix on
them. Details about each option are in the
<application>Perforce</application> docs.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>LineEnd:</literal></term>
<listitem>
<para>This handles CR-LF conversions and should be left to the
default unless you have special needs for it.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>View:</literal></term>
<listitem>
<para>This is where the server-to-local file mappings go. The
default is</para>
<programlisting>//depot/... //<replaceable>client</replaceable>/...</programlisting>
<para>This will map the entire
<application>Perforce</application> repository to the
<filename role="directory">Root</filename> directory of your
client. <emphasis>DO NOT USE THIS DEFAULT!</emphasis> The
&os; repo is huge, and trying to map and sync it all will
take an enormous amount of resources. Instead, only map the
section of the repo that you intend to work on. For
example, there is the smpng project tree at <filename
role="directory">//depot/projects/smpng</filename>. A
mapping for this might look like:</para>
<programlisting>//depot/projects/smpng/... //<replaceable>client</replaceable>/...</programlisting>
<para>The <literal>...</literal> should taken literally. It
is a <application>Perforce</application> idiom for saying
<quote>this directory and all files and directories below
it.</quote></para>
<para>A View can contain multiple mappings. Let's say you
want to map in both the SMPng tree and the NFS tree. Your
View might look like:</para>
<programlisting>//depot/projects/smpng/... //<replaceable>client</replaceable>/smpng/...
//depot/projects/nfs/... //<replaceable>client</replaceable>/nfs/...</programlisting>
<para>Remember that the <replaceable>client</replaceable> is
the name of the client that was specified in the
<literal>Client</literal> section, but in the
<literal>View</literal> it also resolves to the directory
that was specified in the <literal>Root</literal>
section.</para>
<para>Also note that the same file or directory cannot be
mapped multiple times in a single view. The following is
illegal and will produce undefined results:</para>
<programlisting>//depot/projects/smpng/... //<replaceable>client</replaceable>/smpng-foo/...
//depot/projects/smpng/... //<replaceable>client</replaceable>/smpng-bar/...</programlisting>
<para>Views are a tricky part of the learning experience with
<application>Perforce</application>, so do not be afraid to
ask questions.</para>
</listitem>
</varlistentry>
</variablelist>
<para>Existing clients can be listed via the <command>p4
clients</command> command. They can be viewed without being
modified via the <command>p4 client -o
<replaceable>clientname</replaceable></command> command.
<para>Whenever you are interacting with files in
<application>Perforce</application>, the <envar>P4CLIENT</envar>
environment variable must be set to the name of the client that
you are using, like so:</para>
<screen>&prompt.user; <userinput>export P4CLIENT=<replaceable>myclientname</replaceable></userinput></screen>
<para>Note that client mappings in the repository are not exclusive;
multiple clients can map in the same part of the repository. This
allows multiple people to access and modify the same parts of the
repository, allowing a team of people to work together on the same
code.</para>
<sect1 id="syncing">
<title>Syncing</title>
<para>Once you have a client specification defined and the
<envar>P4CLIENT</envar> variable set, the next step is to pull the
files for that client down to your local machine. This is done
with the <command>p4 sync</command> command, which instructs
<application>Perforce</application> to synchronize the local files
in your client with the repository. The first time it runs, it
will download all of the files. Subsequent runs will only
download files that have changed since the previous run. This
allows you to stay in sync with others whom you might be working
with.</para>
<para>Sync operations only work on files that the
<application>Perforce</application> server knows has changed. If
you change or delete a file locally without informing the server,
doing a sync will not bring it back. However, doing a <command>p4
sync -f</command> will unconditionally sync all files, regardless
of their state. This is useful for resolving problems where you
think that your tree might be corrupt.</para>
<para>You can sync a subset of your tree or client by specifying a
relative path to the sync command. For example, to only sync the
<filename role="directory">ufs</filename> directory of the
<literal>smpng</literal> project, you might do the
following:</para>
<screen>&prompt.user; <userinput>cd <replaceable>projectroot</replaceable>/smpng</userinput>
&prompt.user; <userinput>p4 sync src/sys/ufs/...</userinput></screen>
<para>Specifying a local relative path works for many other
<command>p4</command> commands.</para>
<sect1 id="branches">
<title>Branches</title>
<para>One of the strongest features of
<application>Perforce</application> is branching. Branches are
very cheap to create, and moving changes between related branches
is very easy (as will be explained later). Branches also allow
you to do very experimental work in a sandbox-like environment,
without having to worry about colliding with others or
destabilizing the main tree. They also provide insulation against
mistakes while learning the <application>Perforce</application>
system. With all of these benefits, it makes sense for each
project to have its own branch, and we strongly encourage that
with &os;. Frequent submits of changes to the server are also
encouraged.</para>
<para>The <application>Perforce</application> repository (the
<quote>depot</quote>) is a single flat tree. Every file, whether
a unique creation or a derivative from a branch, is accessible via
a simple path under the server <filename
role="directory">//depot</filename> directory. When you create a
branch, all you are doing is creating a new path under the
<filename role="directory">//depot</filename>. This is in sharp
contrast to systems like CVS, where each branch lives in the same
path as its parent. With <application>Perforce</application>, the
server tracks the relationship between the files in the parent and
child, but the files themselves live under their own paths.</para>
<para>The first step to creating a branch is to create a branch
specification. This is similar to a client specification, but is
created via the command <command>p4 branch
<replaceable>branchname</replaceable></command>.</para>
<para>The following important fields are explained:</para>
<variablelist>
<varlistentry>
<term><literal>Branch</literal></term>
<listitem>
<para>The name of the branch. It can be any name, but must be
unique within the repository. The common convention in &os;
is to use
<replaceable>username</replaceable>_<replaceable>projectname</replaceable>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>Description</literal></term>
<listitem>
<para>This can hold a simple text description to describe the
branch.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>View</literal></term>
<listitem>
<para>This is the branch mapping. Instead of mapping from the
depot to the local machine like a client map, it maps between
the branch parent and branch child in the depot. For example,
you might want to create a branch of the smpng project. The
mapping might look like:</para>
<programlisting>//depot/projects/smpng/... //depot/projects/my-super-smpng/...</programlisting>
<para>Or, you might want to create a brand new branch off of
the stock &os; sources:</para>
<programlisting>//depot/vendor/freebsd/... //depot/projects/my-new-project/...</programlisting>
<para>This will map the &os; HEAD tree to your new
branch.</para>
</listitem>
</varlistentry>
</variablelist>
<para>Creating the branch spec only saves the spec itself in the
server, it does not modify the depot or change any files. The
directory that you specified in the branch is empty on the server
until you populate it.</para>
<para>To populate your branch, first edit your client with the
<command>p4 client</command> command and make sure that the branch
directory is mapped in your client. You might need to add a
<literal>View</literal> line like:</para>
<programlisting>//depot/projects/my-new-project/... //<replaceable>myclient</replaceable>/my-new-project/...</programlisting>
<para>The next step is to run the <command>p4 integrate</command>
command, as described in the next section.</para>
<sect1 id="Integrations">
<title>Integrations</title>
<para><quote>Integration</quote> is the term used by
<application>Perforce</application> to describe the action of
moving changes from one part of the depot to another. It is most
commonly done in conjunction with creating and maintaining
branches. An integration is done when you want to initially
populate a branch, and it's done when you want to move subsequent
changes in the branch from the parent to the child, or from the
child to the parent. A common example of this is periodically
integrating changes from the vendor &os; tree to your child branch
tree, allowing you to keep up to date with changes in the &os;
tree. The <application>Perforce</application> server tracks the
changes in each tree and knows when there are changes that can be
integrated from one tree to another.</para>
<para>The common way to do an integration is with the following
command:</para>
<screen>&prompt.user; <userinput>p4 integrate -b <replaceable>branchname</replaceable></userinput></screen>
<para><replaceable>branchname</replaceable> is the name given to a
branch spec, as discussed in the previous section. This command
will instruct <application>Perforce</application> to look for
changes in the branch parent that are not yet in the child. From
those changes it will prepare a list of diffs to move. If the
integration is being done for the first time on a branch (i.e.
doing an initial population operation), then the parent files will
simply be copied to the child location on the local
machine.</para>
<para>Once the integration operation is done, you must run
<command>p4 resolve</command> to accept the changes and resolve
possible conflicts. Conflicts can arise from overlapping changes
that happened in both the parent and child copy of a file.
Usually, however, there are no conflicts, and
<application>Perforce</application> can quickly figure out how to
merge the changes together. Use the following commands to do a
resolve operation:</para>
<screen>&prompt.user; <userinput>p4 resolve -as</userinput>
&prompt.user; <userinput>p4 resolve</userinput></screen>
<para>The first invocation will instruct
<application>Perforce</application> to automatically merge the
changes together and accept files that have no conflicts. The
second invocation will allow you to inspect each file that has a
possible conflict and resolve it by hand if needed.</para>
<para>Once all of the integrated files have been resolved, they need
to be committed back to the repository. This is done via the
<command>p4 submit</command> command, explained in the next
section.</para>
</sect1>
<sect1 id="submit">
<title>Submit</title>
<para>Changes that are made locally should be committed back to the
<application>Perforce</application> server for safe keeping and so
that others can access them. This is done via the <command>p4
submit</command> command. When you run this command, it will open
up a submit template in an editor. &os; has a custom template,
and the important fields are described below:</para>
<programlisting>Description:
&lt;enter description here&gt;
PR:
Submitted by:
Reviewed by:
Approved by:
Obtained from:
MFP4 after:</programlisting>
<para>It is good practice to provide at least 2-3 sentences that
describe what the changes are that you are submitting. You say
should what the change does, why it was done that way or what
problem is solves, and what APIs it might change or other side
effects it might have. This text should replace the
<literal>&lt;enter description here&gt;</literal> line in the template.
You should wrap your lines and start each line with a TAB. The
tags below it are &os;-specific and can be removed if not
needed.</para>
<programlisting>Files:</programlisting>
<para>This is automatically populated with all of the files in your
client that were marked in the add, delete, integrate, or edit
states on the server. It is always a very good idea to review
this list and remove files that might not be ready yet.</para>
<para>Once you save the editor session, the submit will happen to
the server. This also means that the local copies of the
submitted files will be copied back to the server. If anything
goes wrong during this process, the submit will be aborted, and
you will be notified that the submit has been turned into a
changelist that must be corrected and re-submitted. Submits are
atomic, so if one file fails, the entire submit is aborted.</para>
<para>Submits cannot be reverted, but they can be aborted while in
the editor by exiting the editor without changing the
<literal>Description</literal> text.
<application>Perforce</application> will complain about this the
first time you do it and will put you back in the editor. Exiting
the editor the second time will abort the operation. Reverting a
submitted change is very difficult and is best handled on a
case-by-case basis.</para>
</sect1>
<sect1 id="editing">
<title>Editing</title>
<para>The state of each file in the client is tracked and saved on
the server. In order to avoid collisions from multiple people
working on the same file at once,
<application>Perforce</application> tracks which files are opened
for edit, and uses this to help with submit, sync, and integration
operations later on.</para>
<para>To open a file for editing, use the <command>p4 edit</command>
command like so:</para>
<screen>&prompt.user; <userinput>p4 edit <replaceable>filename</replaceable></userinput></screen>
<para>This marks the file on the server as being in the edit state,
which then allows it to be submitted after changes are made, or
marks it for special handling when doing an integration or sync
operation. Note that editing is not exclusive in
<application>Perforce</application>. Multiple people can have the
same file in the edit state (you will be informed of others when
you run the <command>edit</command> command), and you can submit
your changes even when others are still editing the file.</para>
<para>When someone else submits a change to a file that you are
editing, you will need to resolve his changes with yours before
your submit will succeed. The easiest way to do this is to either
run a <command>p4 sync</command> or <command>p4 submit</command>
and let it fail with the conflict, then run <command>p4
resolve</command> to manually resolve and accept his changes into
your copy, then run <command>p4 submit</command> to commit your
changes to the repository.</para>
<para>If you have a file open for edit and you want to throw away
your changes and revert it to its original state, run the
<command>p4 revert</command> command like so:</para>
<screen>&prompt.user; <userinput>p4 revert <replaceable>filename</replaceable></userinput></screen>
<para>This resyncs the file to the contents of the server, and
removes the edit attribute from the server. Any local changes
that you had will be lost. This is quite useful when you have a
made changes to a file but later decide that you do not want to
keep them.</para>
<para>When a file is synced, it is marked read-only in the
filesystem. When you tell the server to open it for editing, it
is changed to read-write on the filesystem. While these
permissions can easily be overridden by hand, they are meant to
gently remind you that you should being using the <command>p4
edit</command> command. Files that have local changes but are not
in the edit state may get overwritten when doing a <command>p4
sync</command>.</para>
</sect1>
<sect1 id="changes">
<title>Changes, Descriptions, and History</title>
<para>Changes to the <application>Perforce</application> depot can
be listed via the <command>p4 changes</command> command. This
will provide a brief description of each change, who made the
change, and what its change number was. A change can be examined
in detail via the <command>p4 describe
<replaceable>changenumber</replaceable></command> command. This
will provide the submit log and the diffs of the actual change.
It is common to use the <option>-du</option> or
<option>-dc</option> flags to produce unified or context diffs
instead of the native diff format.</para>
<para>The <command>p4 filelog
<replaceable>filename</replaceable></command> command will show
the history of a file, including all submits, integrations, and
branches of it.</para>
</sect1>
<sect1 id="diffs">
<title>Diffs</title>
<para>There are two methods of producing file diffs in
<application>Perforce</application>, either against local changes
that have not been submitted yet, or between two trees (or within
a branch) in the depot. These are done with different commands,
<option>diff</option> and <option>diff2</option>:</para>
<variablelist>
<varlistentry>
<term><command>p4 diff</command></term>
<listitem>
<para>This generates a diff of the local changes to files in
the edit state. The <option>-du</option> and
<option>-dc</option> flags can be used to create unified or
context diffs, respectively, or the <envar>P4DIFF</envar>
environment variable can be set to a local diff command to be
used instead. It is a very good idea to use this command to
review your changes before submitting them.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><command>p4 diff2</command></term>
<listitem>
<para>This creates a diff between arbitrary files in the
depot, or between files specified in a branch spec. The diff
operation takes place on the server, so <envar>P4DIFF</envar>
variable has no effect, though the <option>-du</option> and
<option>-dc</option> flags do work. The two forms of this
command are:</para>
<screen>&prompt.user; <userinput>p4 diff2 -b <replaceable>branchname</replaceable></userinput></screen>
<para>and</para>
<screen>&prompt.user; <userinput>p4 diff2 //depot/<replaceable>path1</replaceable> //depot/<replaceable>path2</replaceable></userinput></screen>
</listitem>
</varlistentry>
</variablelist>
<para>In all cases the diff will be written to the standard output.
Unfortunately, <application>Perforce</application> produces a diff
format that is slightly incompatible with the traditional Unix
diff and patch tools. Using the <envar>P4DIFF</envar> variable to
point to the real &man.diff.1; tool can help this, but only for
the <command>p4 diff</command> command. The output of
<option>diff2</option> command must be post-processed to be useful
(the <option>-u</option> flag of <option>diff2</option> will
produce unified diffs that are somewhat compatible, but it does
not include files that have been added or deleted). There is a
post-processing script at: <ulink
url="http://people.freebsd.org/~scottl/awkdiff"></ulink>.</para>
</sect1>
<sect1 id="add-rm-files">
<title>Adding and Removing Files</title>
<para>Integrating a branch will bring existing files into your tree,
but you may still want to add new files or remove existing ones.
Adding files is easily done be creating the file and then running
the <command>p4 add</command> command like so:</para>
<screen>&prompt.user; <userinput>p4 add <replaceable>filename</replaceable></userinput></screen>
<para>If you want to add a whole tree of files, run a command
like:</para>
<screen>&prompt.user; <userinput>find . -type f |xargs p4 add</userinput></screen>
<para>Doing a <command>p4 submit</command> will then copy the file
to the Depot on the server. It is very important to only add
files, not directories. Explicitly adding a directory will cause
<application>Perforce</application> to treat it like a file, which
is not what you want.</para>
<para>Removing a file is just as easy with the <command>p4</command>
delete command like so:</para>
<screen>&prompt.user; <userinput>p4 delete <replaceable>filename</replaceable></userinput></screen>
<para>This will mark the file for deletion from the Depot the next
time that a submit is run. It will also remove the local copy of
the file, so beware.</para>
<para>Of course, deleting a file does not actually remove it from
the repository.</para>
<para>Deleted files can be resurrected by syncing them to a prior
version. The only way to permanently remove a file is to use the
<command>p4 obliterat</command>e command. This command is
irreversible and expensive, so it is only available to those with
admin access.</para>
</sect1>
<sect1 id="working-with-diffs">
<title>Working with diffs</title>
<para>Sometimes you might need to apply a diff from another source
to a tree under <application>Perforce</application> control. If
it is a large diff that affects lots of files, it might be
inconvenient to manually run <command>p4 edit</command> on each
file. There is a trick for making this easier. First, make sure
that no files are open on your client and that your tree is synced
and up to date. Then apply the diff using the normal tools, and
coerce the permissions on the files if needed. Then run the
following commands:</para>
<screen>&prompt.user; <userinput>p4 diff -se ... |xargs p4 edit</userinput>
&prompt.user; <userinput>p4 diff -sd ... |xargs p4 delete</userinput>
&prompt.user; <userinput>find . -type f |xargs p4 add</userinput></screen>
<para>The first command tells <application>Perforce</application> to
look for files that have changed, even if they are not open. The
second command tells <application>Perforce</application> to look
for files that no longer exist on the local machine but do exist
on the server. The third command then attempts to add all of the
files that it can find locally. This is a very brute-force
method, but it works because <application>Perforce</application>
will only add the files that it does not already know about. The
result of running these commands will be a set of files that are
opened for edit, removal, or add, as appropriate. Just do a
<command>p4 submit</command> after that.</para>
</sect1>
<sect1 id="renaming-files">
<title>Renaming files</title>
<para><application>Perforce</application> does not have a built-in
way of renaming files or moving them to a different part of the
tree. Simply copying a file to the new location, doing a
<command>p4 add</command> on it, and a <command>p4
delete</command> on the old copy, works, but does not preserve
change history of the file. This can make future integrations
with parents and children very bumpy, in fact. A better method of
dealing with this is to do a one-time, in-tree integration, like
so:</para>
<screen>&prompt.user; <userinput>p4 integrate -i <replaceable>oldfile</replaceable> <replaceable>newfile</replaceable></userinput>
&prompt.user; <userinput>p4 resolve</userinput>
&prompt.user; <userinput>p4 delete <replaceable>oldfile</replaceable></userinput>
&prompt.user; <userinput>p4 submit</userinput></screen>
<para>The integration will force <application>Perforce</application>
to keep a record of the relationship between the old and new
names, which will assist it in future integrations. The
<option>-i</option> flag tells it that it is a
<quote>baseless</quote> integration, meaning that there is no
branch history available for it to use in the integration. That
is perfect for an integration like this, but should not be used
for normal branch-based integrations.</para>
</sect1>
<sect1 id="freebsd-cvs-and-p4">
<title>Interactions between &os; CVS and Perforce</title>
<para>The &os; <application>Perforce</application> and CVS
repositories are completely separate. However, changes to CVS are
tracked at near-real-time in <application>Perforce</application>.
Every 2 minutes, the CVS server is polled for updates in the HEAD
branch, and those updates are committed to
<application>Perforce</application> in the <filename
role="directory">//depot/vendor/freebsd/...</filename> tree. This
tree is then available for branching and integrating to derivative
projects. Any project that directly modifies that &os; source
code should have this tree as its branch parent (or grandparent,
depending on the needs), and periodic integrations and syncs
should be done so that your tree stays up to date and avoids
conflicts with mainline development.</para>
<para>The bridge between CVS and <application>Perforce</application>
is one-way; changes to CVS will be reflected in
<application>Perforce</application>, but changes in Perforce will
not be reflected in CVS. On request, some parts of the
<application>Perforce</application> repo can be exported to
<application>CVSup</application> and made available for
distribution that way. Contact the &os;
<application>Perforce</application> administrators if this is
something that you are interested in.</para>
</sect1>
<sect1 id="offline-ops">
<title>Offline Operation</title>
<para>One weakness of <application>Perforce</application> is that it
assumes that network access to the server is always available.
Most state, history, and metadata is saved on the server, and
there is no provision for replicating the server like there is
with CVS/<application>CVSup</application>. It is possible to run
a proxy server, but it only provides very limited utility for
offline operation.</para>
<para>The best way to work offline is to make sure that your client
has no open files and is fully synced before going offline. Then
when editing a file, manually change the permissions to
read-write. When you get back online, run the commands listed in
the <xref linkend="working-with-diffs"> to automatically identify
files that have been edited, added, and removed. It is quite
common to be surprised by <application>Perforce</application>
overwriting a locally changed file that was not opened for edit,
so be extra vigilant with this.</para>
</sect1>
<sect1 id="soc">
<title>Notes for Google Summer of Code</title>
<para>Most &os; projects under the Google Summer of Code program
will be based in <filename
role="directory">//depot/projects/soc2005/<replaceable>project-name</replaceable>/...</filename>
on the &os; <application>Perforce</application> server.</para>
<para>The project mentor is responsible for choosing a suitable
project name and getting the student going with
<application>Perforce</application>.</para>
<para>Access to the &os; <application>Perforce</application> server
does not imply membership in the &os; CVS committer community,
though we happily encourage all students to consider joining the
project when the time is appropriate.</para>
</sect1>
</article>