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Re: Overwriting trunk files with specific branch files

From: Jim Hyslop
Subject: Re: Overwriting trunk files with specific branch files
Date: Wed, 17 Aug 2005 12:34:07 -0400
User-agent: Mozilla Thunderbird 1.0.2 (Windows/20050317)

Andy Jones wrote:
cvs co -j HEAD -j t_branchA_tagA module

Does anyone feel like explainaing how this is not a merge?  I don't get it.

It is a merge command, but it does not merge the changes from the branch. It will overwrite the head with the branch.

The command as shown is a shortcut to:

cvs co module
cd module
cvs up -j HEAD -j t_branchA_tagA

"cvs up -j REVA -j REVB", the merge command, applies the delta between REVB and REVA to the current directory. For a normal merge, REVA and REVB are normally on the same branch, thus you would get the changes from the branch merged into the changes on the trunk, i.e. trunk = trunk + branch. But, in this case, REVA and REVB refer to the tip revisions on two different branches. The delta is Branch-HEAD, which when added to the HEAD, results in Branch.

Mathematically, this can be expressed as:

CWD = CWD + Delta

where CWD is the current working directory, and Delta is REVB - REVA. In this example CWD is HEAD, REVA is HEAD and REVB is Branch, so the equation becomes:

CWD = HEAD + Branch - HEAD

which simplifies to

CWD = Branch

It takes a bit to wrap your head around it, but it does work and do exactly what Christopher wanted.


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