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(cvs.info)Branches and revisions

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Branches and revisions
======================

   Ordinarily, a file's revision history is a linear series of
increments (Note: Revision numbers):

            +-----+    +-----+    +-----+    +-----+    +-----+
            ! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !----! 1.5 !
            +-----+    +-----+    +-----+    +-----+    +-----+

   However, CVS is not limited to linear development.  The "revision
tree" can be split into "branches", where each branch is a
self-maintained line of development.  Changes made on one branch can
easily be moved back to the main trunk.

   Each branch has a "branch number", consisting of an odd number of
period-separated decimal integers.  The branch number is created by
appending an integer to the revision number where the corresponding
branch forked off.  Having branch numbers allows more than one branch
to be forked off from a certain revision.

   All revisions on a branch have revision numbers formed by appending
an ordinal number to the branch number.  The following figure
illustrates branching with an example.

                                                           +-------------+
                                Branch 1.2.2.3.2 ->        ! 1.2.2.3.2.1 !
                                                         / +-------------+
                                                        /
                                                       /
                      +---------+    +---------+    +---------+
     Branch 1.2.2 -> _! 1.2.2.1 !----! 1.2.2.2 !----! 1.2.2.3 !
                    / +---------+    +---------+    +---------+
                   /
                  /
     +-----+    +-----+    +-----+    +-----+    +-----+
     ! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !----! 1.5 !  <- The main trunk
     +-----+    +-----+    +-----+    +-----+    +-----+
                     !
                     !
                     !   +---------+    +---------+    +---------+
     Branch 1.2.4 -> +---! 1.2.4.1 !----! 1.2.4.2 !----! 1.2.4.3 !
                         +---------+    +---------+    +---------+

   The exact details of how the branch number is constructed is not
something you normally need to be concerned about, but here is how it
works: When CVS creates a branch number it picks the first unused even
integer, starting with 2.  So when you want to create a branch from
revision 6.4 it will be numbered 6.4.2.  All branch numbers ending in a
zero (such as 6.4.0) are used internally by CVS (Note: Magic branch
numbers).  The branch 1.1.1 has a special meaning.  Note: Tracking
sources.