Does perforce track deltas unique to a changeset or does it just store the whole file?

Question

I tried to merge some work that a developer did in a working branch to a stable branch. The files a, b, and c had been changed by at least a dozen changesets since the common ancestor of STABLE and HEAD branches were separated.

I expected that since this developer changed five lines in each of file a, b, and c, that when I integrated from the HEAD to the STABLE branch, I would get his changes in my pending changset, which I could then review and commit.

Instead, it seems that it has taken every change that happened to file A, since the two were branched, and applied all of those changes that also existed in my colleague's working copy.

In other words, there seems to be no record in a perforce changeset, of what my colleague actually changed, versus what the file before contained.

If I browse the submitted changesets, I can see the difference between my colleague's version of the file, and the immediately preceding version. But then, that does not, it seems, determine what goes into the merge.

Doesn't a changeset mean, "a set of changes made between rev X and revision X+1 of a file"? Can anybody help me understand what it means to "integrate a changeset" when in fact, what it seems is that Perforce doesn't track changes, it tracks files.

It is entirely possible that I am doing everything wrong, and would appreciate any pointer as to how it is that you can can merge accurately and safely between Perforce working branches and stable branches, without stuff that you don't want to get integrated to the stable branch getting integrated. It seems that no matter how simple the changes that actually get made in the product, the merge does not actually work for me.

Answer 1

Perforce does save changes to text files as deltas (binary files get saved in their entirety every time a change is submitted). It sounds like you're not properly restricting the revision range during your integration.

You say the working branch has "...been changed by at least a dozen changesets since the ...branches were separated." Let's call them changelists 1-12. If I understand you correctly you are trying to integrate the modifications made in just one of those changelists, not all of them.

During a simple integration operation Perforce will assume you want to integrate all of the changes that have been submitted since the branch was made. If you only want a subset of these changes, you have to specify a revision range. So, if you just want to integrate the changes that occurred between changelist 11 and 12, you would specify that revision range as shown in the screen capture. (Note: the revision range is inclusive, so specifying a range of 11-12, as I do in this screen shot will actually include changes in changelists 11 and 12. If you just want to integrate the changes made in changelist 12, enter 12 in both fields of the revision range.)

Just be aware that the inevitable conflicts that arise may be difficult to resolve, depending upon how far the branches have diverged and the nature of the changes.

Answer 2

Could you be more specific on how you did the integration? My guess is that you probably have integrated all the changes up to that changelist instead of just that changelist only. If so all you need to do is to specify the same changelist as both the upper and lower limit of the integration.

It's very easy to do in the visual client, but I'm not sure of the exact command line switch you need to use.