Merge Example in <version-goals-01221999.htm>

Sean Shapira (
Fri, 22 Jan 1999 20:58:20 -0800 (PST)

Message-Id: <>
From: (Sean Shapira)
Date: Fri, 22 Jan 1999 20:58:20 -0800 (PST)
Subject: Merge Example in <version-goals-01221999.htm>

The <version-goals-01221999.htm> draft provides an excellent
fictitious example of a version control system in use, showing
how "activities" are used to prepare for later merges.  But the 
example does not make clear where merged revisions appear in the 
revision histories of versioned resources.

As it happens, this fictitious usage scenario also provides an 
excellent opportunity for discussion of some apparent weaknesses 
in "first checkout is special" revision control systems.

The example describes a user named Joe who began doing some work
in the "mainline" activity, and a user named Jane who later began
work on the same versioned resource in a separate "image_updates" 
activity.  When Joe attempts to merge the activities, "There are 
a number of places where he added new functions that do not have 
images as Jane didn't know they were there."  Nonetheless, "Once 
the changes are complete, Joe checks in the merged version."

But version-goals-01221999.htm does not make clear where in the 
is-derived-from graph Joe's merged revision appears.  Given that
it lacks some needed images, the new revision apparently belongs 
at the tip of the branch associated with the image_updates activity.  
It doesn't yet belong on the mainline branch since not all the 
image update work has been done.  But once the new revision has 
been placed in the image_updates branch, Jane can easily see Joe's 
new functions and add the images they need.

While this approach does work, I assert it is unfair to Jane.  She 
completed her work before Joe completed his.  Why wasn't her work 
added back into the mainline?  She was done, and could have created
a mainline revision that made her work more publically available.  
Yet as I understand the system proposed, she could not do this because 
Joe, by mere virtue of having checked out the file first, claimed the 
right to check in first as well.

Did I read the proposal correctly in this regard?

Sean Shapira         +1 206 443 2028
               Serving the Net since 1990.