Re: CVS merge issue: "cvs update -j -j"

[Glen Wolfe]

Hi guys

Excuse me for intruding
on your discussion .... I am a colleague of Frederic's and was interested
in your reply, BJ (I hope you don't mind the abbreviation ) ...

I am trying to reconcile
my image of the merge process with the balancing concepts you use.

The image in my mind
of the merge (from our use of it I guess) is something like:

                  0  Initial
revision
                  |
                  |
                  0  RevA
                  |\
                  | \
                  |  ------------0
 RevB
                  |  
           |
                  |  
           |
                  |  
           |
                  |  
           0  RevD     
                  |  
           |           
                  |  
           |           
                   |
             |
                   |
             0  RevE     a
                  |  
           |           b
                  |  
           |           c
                  |  
           |           
                  |  
           |           
                  |  
           |           
                   |
             0  RevF     a
                  |  
           |           b
                  |  
           |           c
                   |
             |           d
                  |              |           e
                   |
             |
                  0  RevC  a     0  RevG     
                                             
                                             

Our objective is to take
the change between RevE and RevF and apply it to RevC
- as we understand, to merge the delta from RevE to RevF with RevC
- cvs update -jRevE -jRevF


From what I understand
you to say, the situation could be one of two general cases, either:

CASE #1

                   0
 Initial revision
                  |
                  |  
        x
                   |
          y
                   |
          z
                   0
 RevA     a
                   |\
         b
                   |
\         c  
                   |
 ------------0  RevB
                   |
             |
   transition is   |
             |--- transition is to remove lines x,y,z, replace 
line b with p
   to remove    ---|        
     |    and add lines q,r
   lines x,y,z,b,c |
             0  RevD     a
                   |
             |           p
                   |
             |           c      --- transition is to replace line p with
b
                    |
             |           q          and 
remove lines q,r
                    |      
       |           r
                    |
             |
                  |         
    0  RevE     a
                   |
             |           b
                   |
             |           c
                   |
             |                  --- transition is to add lines d,e
                   |
             |           
                   |
             |           
                    |
             0  RevF     a
                   |
             |           b
                   |
             |           c
                    |
             |           d
                    |
             |           e
                    |
             |
                  0  RevC  a
    0  RevG


or

CASE #2

                   0
 Initial revision
                  |
                  |  
        
                   |
          a
                   |
          x
                   0
 RevA     y
                   |\
         z
                   |
\           
                   |
 ------------0  RevB
                   |
             |
   transition is   |
             |--- transition is to remove lines x,y,z and add lines p,c,q,r
   to remove    ---|
             |
   lines x,y,z     |
             0  RevD     a
                   |
             |           p
                   |
             |           c      --- transition is to replace p with b
                    |
             |           q          and 
remove lines q,r
                    |      
       |           r
                    |
             |
                  |         
    0  RevE     a
                   |
             |           b
                   |
             |           c
                   |
             |                  --- transition is to add lines d,e
                   |
             |           
                   |
             |           
                    |
             0  RevF     a
                   |
             |           b
                   |
             |           c
                    |
             |           d
                    |
             |           e
                    |
             |
                  0  RevC  a
    0  RevG


In our use of the function,we wish to transfer the functionality represented
by the change from RevE to RevF without taking the functionality delivered
as the changes from RevA to RevE.
 
I am having trouble seeing your point of view that the addition of lines
b,c on one branch or the removal on the other makes any difference to the
result. True, either may have been performed in error, but so may any of
the other revision transitions which are not displayed as involved in this
merge.

Can you help me to understand your idea of what the merge objectives are
and how the path to each revision is important to you?

> Frederic Gioanni writes:
>   
> >  
> >   Hi,
> >     
> > I have got some problems when merging delta between rev1 and rev2 into
> > my Working revision of a file using
> >     cvs  update  -j  rev1  -j  rev2  file
> >     
> > I am using CVS 1.10 with diff3 2.7. The same problem occurs in the
> > latest version of CVS.
> >     
> > Let's say that the content of file:rev1 is:
> >     
> >     a
> >     b
> >     c
> >     
> > Content of file:rev2 is:
> >     
> >     a
> >     b
> >     c
> >     d
> >     e
> >     
> > Content of my working revision is:
> >     
> >     a
> >     
> > When doing the merge, I am expecting 2 new lines and so I am expecting
> > the following conflict:
> >     
> >     a
> >     <<<<<<< file
> >     =======
> >     d
> >     e
> >     >>>>>>> rev2
> >     
>
> When two changes conflict, a merge utility should add conflict markers
> that show both of the changes.  But the above file shows only one of
> the changes, namely the addition of d and e.  But it does not show the
> deletion of b and c even though that deletion conflicted with the
> other change.
>     
> I.e., the above file is biased in favor of one of the two new revisions
> of the file.  An analogy of this would be how newspapers often have a
> policy that they will report both sides of an issue so as to be fair.
> For example, if there is conflict between two senators, where one
> senator offers a reason in support of a bill and another senator
> offers a reason to be opposed to it, then to be fair, the newspaper
> should quote both of the senators.  If it quotes only one senator,
> then reader might think that argument makes sense and the reader might
> not know of any opposing arguments.  If the reader knew about opposing
> arguments he might change his mind.
>     
> This is analogous to how the person resolving the conflict in the
> above file will not know that anyone deleted b and c.  But suppose
> that that deletion was a mistake.  If only the person who is resolving
> the conflict knew that someone deleted it, then he might realize that
> that person made a mistake.  The above file will not help him notice
> that mistake which means the mistake would remain uncorrected.  The
> file below is better because it does show that someone may have
> mistakingly deleted b and c.
>     
>     
> > However, "cvs up -j -j" ends with:
> >       
> >     a
> >     <<<<<<< file
> >     =======
> >     b
> >     c
> >     d
> >     e
> >     >>>>>>> rev2
> >       
> > When resolving the conflict, the user thinks that 4 lines were added
> > between rev1 and rev2 whereas only 2 lines were added.
> >       
>
> Whenever one version of a file has some text which another file does
> not have, it can always be interpreted in two ways: either someone
> added the text to one file or someone deleted the text from the other
> file.  The user in your example is mistaken if he does not consider
> both possibilities.  When cvs made the file above, cvs did not imply
> one interpretation over another.  Therefore the user should likewise not
> assume one interpretation must be the right one based on only seeing
> the above file.  However, the user will have other information which can
> help him decide which interpretation is correct.  Specially, the user
> will remember what changes he made so he will know whether he added or
> deleted anything.  Knowing that will help him know if the other file
> added or deleted anything.  Therefore, he can figure out which
> interpretation is correct.  And if he forgets what changes he made, he
> can ask cvs to show him the complete file of rev1.  That will make it easy
> to see whether these changes are additions or deletions.
>       
> So, in my opinion, CVS is acting correctly.
>

--

Enjoy! Dr Glen Wolfe Tools and Methods Engineer Thales ATM Melbourne Australia

strength in elegance beauty in intelligence    - dig