Multiple developers
*******************

   When more than one person works on a software project things often
get complicated.  Often, two people try to edit the same file
simultaneously.  One solution, known as "file locking" or "reserved
checkouts", is to allow only one person to edit each file at a time.
This is the only solution with some version control systems, including
RCS and SCCS.  Currently the usual way to get reserved checkouts with
CVS is the `cvs admin -l' command (see admin options.).  This is
not as nicely integrated into CVS as the watch features, described
below, but it seems that most people with a need for reserved checkouts
find it adequate.  It also may be possible to use the watches features
described below, together with suitable procedures (not enforced by
software), to avoid having two people edit at the same time.

   The default model with CVS is known as "unreserved checkouts".  In
this model, developers can edit their own "working copy" of a file
simultaneously.  The first person that commits his changes has no
automatic way of knowing that another has started to edit it.  Others
will get an error message when they try to commit the file.  They must
then use CVS commands to bring their working copy up to date with the
repository revision.  This process is almost automatic.

   CVS also supports mechanisms which facilitate various kinds of
communcation, without actually enforcing rules like reserved checkouts
do.

   The rest of this chapter describes how these various models work,
and some of the issues involved in choosing between them.

Menu

File status

A file can be in several states

Updating a file

Bringing a file up-to-date

Conflicts example

An informative example

Informing others

To cooperate you must inform

Concurrency

Simultaneous repository access

Watches

Mechanisms to track who is editing files

Choosing a model

Reserved or unreserved checkouts?