=head1 NAME

repository - Using the Perl repository

This document describes what a Perl Porter needs to do
to start using the Perl repository.

=head1 Prerequisites

You'll need to get hold of the following software.

=over 4

=item Perforce

Download a perforce client from:

   http://www.perforce.com/perforce/loadprog.html

You'll probably also want to look at:

   http://www.perforce.com/perforce/technical.html

where you can look at or download its documentation.

=item ssh

If you don't already have access to an ssh client, then look at its
home site C<http://www.cs.hut.fi/ssh> which mentions ftp sites from
which it's available. You only need to build the client parts (ssh
and ssh-keygen should suffice).

=back

=head1 Creating an SSH Key Pair

If you already use ssh and want to use the same key pair for perl
repository access then you can skip the rest of this section.
Otherwise, generate an ssh key pair for use with the repository
by typing the command

    ssh-keygen

After generating a key pair and testing it, ssh-keygen will ask you
to enter a filename in which to save the key. The default it offers
will be the file F<~/.ssh/identity> which is suitable unless you
particularly want to keep separate ssh identities for some reason.
If so, you could save the perl repository private key in the file
F<~/.ssh/perl>, for example, but I will use the standard filename
in the remainder of the examples of this document.

After typing in the filename, it will prompt you to type in a
passphrase. The private key will itself be encrypted so that it is
usable only when that passphrase is typed. (When using ssh, you will
be prompted when it requires a pass phrase to unlock a private key.)
If you provide a blank passphrase then no passphrase will be needed
to unlock the key and, as a consequence, anyone who gains access to
the key file gains access to accounts protected with that key
(barring additional configuration to restrict access by IP address).

When you have typed the passphrase in twice, ssh-keygen will confirm
where it has saved the private key (in the filename you gave and
with permissions set to be only readable by you), what your public
key is (don't worry: you don't need to memorise it) and where it
has saved the corresponding public key. The public key is saved in
a filename corresponding to your private key's filename but with
".pub" appended, usually F<~/.ssh/identity.pub>. That public key
can be (but need not be) world readable. It is not used by your
own system at all.

=head1 Notifying the Repository Keeper

Mail the contents of that public key file to the keeper of the perl
repository (see L</Contact Information> below).
When the key is added to the repository host's configuration file,
you will be able to connect to it with ssh by using the corresponding
private key file (after unlocking it with your chosen passphrase).

=head1 Connecting to the Repository

Connections to the repository are made by using ssh to provide a
TCP "tunnel" rather than by using ssh to login to or invoke any
ordinary commands on the repository. When you want to start a
session using the repository, use the command

    ssh -l perlrep -f -q -x -L 1666:127.0.0.1:1666 sickle.activestate.com 
foo

If you are not using the default filename of F<~/.ssh/identity>
to hold your perl repository private key then you'll need to add
the option B<-i filename> to tell ssh where it is. Unless you chose
a blank passphrase for that private key, ssh will prompt you for the
passphrase to unlock that key. Then ssh will fork and put itself
in the background, returning you (silently) to your shell prompt.
The tunnel for repository access is now ready for use.

For the sake of completeness (and for the case where the chosen
port of 1666 is already in use on your machine), I'll briefly
describe what all those ssh arguments are for.

=over 4

=item B<-l perl>

Use a remote username of perl. The account on the repository which
provides the end-point of the ssh tunnel is named "perl".

=item B<-f>

Tells ssh to fork and remain running in the background. Since ssh
is only being used for its tunnelling capabilities, the command
that ssh runs never does any I/O and can sit silently in the
background.

=item B<-q>

Tells ssh to be quiet. Without this option, ssh will output a
message each time you use a p4 command (since each p4 command
tunnels over the ssh connection to reach the repository).

=item B<-x>

Tells ssh not to bother to set up a tunnel for X11 connections.
The repository doesn't allow this anyway.

=item B<-L 1666:127.0.0.1:1666>

This is the important option. It tells ssh to listen out for
connections made to port 1666 on your local machine. When such
a connection is made, the ssh client tells the remote side
(the corresponding ssh daemon on the repository) to make a
connection to IP address 127.0.0.1, port 1666. Data flowing
along that connection is tunnelled over the ssh connection
(encrypted). The perforce daemon running on the repository
only accepts connections from localhost and that is exactly
where ssh-tunnelled connections appear to come from.

If port 1666 is already in use on your machine then you can
choose any non-privileged port (a number between 1024 and 65535)
which happens to be free on your machine. It's the first of the
three colon separated values that you should change. Picking
port 2345 would mean changing the option to
B<-L 2345:127.0.0.1:1666>. Whatever port number you choose should
be used for the value of the P4PORT environment variable (q.v.).

=item sickle.activestate.com

This is the canonical IP name of the host on which the perl
repository runs. Its IP number is 199.60.48.20.

=item foo

This is a dummy place holder argument. Without an argument
here, ssh will try to perform an interactive login to the
repository which is not allowed. Ordinarily, this argument
is for the one-off command which is to be executed on the
remote host. However, the repository's ssh configuration
file uses the "command=" option to force a particular
command to run so the actual value of the argument is
ignored. The command that's actually run merely pauses and
waits for the ssh connection to drop, then exits.

=back

=head1 Problems

You should normally get a prompt that asks for the passphrase
for your RSA key when you connect with the ssh command shown
above.  If you see a prompt that looks like:

    perlrep@sickle.activestate.com's password:

Then you either don't have a ~/.ssh/identity file corresponding
to your public key, or your ~/.ssh/identity file is not readable.
Fix the problem and try again.

=head1 Using the Perforce Client

Remember to read the documentation for Perforce. You need
to make sure that three environment variable are set
correctly before using the p4 client with the perl repository.

=over 4

=item P4PORT

Set this to localhost:1666 (the port for your ssh client to listen on)
unless that port is already in use on your host. If it is, see
the section above on the B<-L 1666:127.0.0.1:1666> option to ssh.

=item P4CLIENT

The value of this is the name by which Perforce knows your
host's workspace. You need to pick a name (for example, your
hostname unless that clashes with someone else's client name)
when you first start using the perl repository and then
stick with it. If you connect from multiple hosts (with
different workspaces) then maybe you could have multiple
clients. There is a licence limit on the number of perforce
clients which can be created. Although we have been told that
Perforce will raise our licence limits within reason, it's
probably best not to use additional clients unless needed.

Note that perforce only needs the client name so that it can
find the directory under which your client files are stored.
If you have multiple hosts sharing the same directory structure
via NFS then only one client name is necessary.

The C<p4 clients> command lists all currently known clients.

=item P4USER

This is the username by which perforce knows you. Use your
username if you have a well known or obvious one or else pick
a new one which other perl5-porters will recognise. There is
a licence limit on the number of these usernames. Perforce
doesn't enforce security between usernames. If you set P4USER
to be somebody else's username then perforce will believe you
completely with regard to access control, logging and so on.

The C<p4 users> command lists all currently known users.

=back

Once these three environment variables are set, you can use the
perforce p4 client exactly as described in its documentation.
After setting these variables and connecting to the repository
for the first time, you should use the C<p4 user> and
C<p4 client> commands to tell perforce the details of your
new username and your new client workspace specifications.

=head1 Ending a Repository Session

When you have finished a session using the repository, you
should kill off the ssh client process to break the tunnel.
Since ssh forked itself into the background, you'll need to use
something like ps with the appropriate options to find the ssh
process and then kill it manually. The default signal of
SIGTERM is fine.

=head1 Overview of the Repository

Please read at least the introductory sections of the Perforce
User Guide (and perhaps the Quick Start Guide as well) before
reading this section.

Every repository user typically "owns" a "branch" of the mainline
code in the repository.  They hold the "pumpkin" for things in this
area, and are usually the only user who will modify files there.
This is not strictly enforced in order to allow the flexibility
of other users stealing the pumpkin for short periods with the
owner's permission.

Here is the current structure of the repository:

    /----+-----perl                  - Mainline development (bleadperl)
         +-----cfgperl               - Configure Pumpkin's Perl
         +-----vmsperl               - VMS Pumpkin's Perl
         +-----maint-5.004------perl - Maintainance branches
         +-----maint-5.005------perl
         +-----maint-5.6------perl

Perforce uses a branching model that simply tracks relationships
between files.  It does not care about directories at all, so
any file can be a branch of any other file--the fully qualified
depot path name (of the form //depot/foo/bar.c) uniquely determines
a file for the purpose of establishing branching relationships.
Since a branch usually involves hundreds of files, such relationships
are typically specified en masse using a branch map (try `p4 help branch`).
`p4 branches` lists the existing branches that have been set up.
`p4 branch -o branchname` can be used to view the map for a particular
branch, if you want to determine the ancestor for a particular set of
files.

The mainline (aka "trunk") code in the Perl repository is under
"//depot/perl/...".  Most branches typically map its entire
contents under a directory that goes by the same name as the branch
name.  Thus the contents of the cfgperl branch are to be found
in //depot/cfgperl.

Run `p4 client` to specify how the repository contents should map to
your local disk.  Most users will typically have a client map that
includes at least their entire branch and the contents of the mainline.

Run `p4 changes -l -m10` to check on the activity in the repository.
//depot/perl/Porting/genlog is useful to get an annotated changelog
that shows files and branches.  You can use this listing to determine
if there are any changes in the mainline that you need to merge into
your own branch.  A typical merging session looks like this:

    % cd ~/p4view/cfgperl
    % p4 integrate -b cfgperl    # to bring parent changes into cfgperl
    % p4 resolve -a ./...        # auto merge the changes
    % p4 resolve ./...           # manual merge conflicting changes
    % p4 submit ./...            # check in

If the owner of the mainline wants to bring the changes in cfgperl
back into the mainline, they do:

    % p4 integrate -r -b cfgperl
    ...

Generating a patch for change#42 is done as follows:

    % p4 describe -du 42 | p4desc | p4d2p > change-42.patch

p4desc and p4d2p are to be found in //depot/perl/Porting/.

=head1 Contact Information

The mail alias <perl-repository-keepers@perl.org> can be used to reach
all current users of the repository.

The repository keeper is currently Gurusamy Sarathy
<gsar@activestate.com>.

=head1 AUTHORS

Malcolm Beattie, mbeattie@sable.ox.ac.uk, 24 June 1997.

Gurusamy Sarathy, gsar@activestate.com, 8 May 1999.

Slightly updated by Simon Cozens, simon@brecon.co.uk, 3 July 2000

=cut