Stefan Sperling wrote: > On Wed, Jul 20, 2011 at 01:13:09PM +0100, Julian Foad wrote: > > There are (broadly speaking) two ways we could perform a "re-integrate" > > merge. The "general" way is to do it by using a sufficiently clever > > general-purpose merge algorithm to merge all the changes that are unique > > to the branch, onto the trunk. The "special" way is to recognize that, > > if the branch is up to date with trunk, then the desired state of the > > trunk is exactly the current state of the branch, so all we need to do > > is make the trunk look like the branch, which is theoretically a trivial > > operation. [...] > I think the above description simplifies things a bit too much > for the purpose of this discussion. [...] > A re-integrate does not simply swap out the trunk with the branch. > It runs a two-URL merge with parameters constructed in such a > way that the delta being merged contains exactly the changes > committed for the feature, and no unrelated changes. [...] > feature +-------------------------------R > / . \ > / .............. \ > / . v > trunk ------+--------------------L------------------o > rW rX > > In the diagram above, L marks the left side of the merge (trunk@X), > and R marks the right side of the merge (feature@HEAD). The difference > between the left and right side is merged into the target.
Ah... I didn't realize it is that flexible. Thanks for correcting me. That's very useful for anyone trying to re-integrate onto a "busy" trunk. > > Note that a practical benefit of the work flow using the "special" > > re-integrate is it ensures the reintegration will not generate any merge > > conflicts - neither physical, nor semantic (since we assume the branch > > has been reviewed and tested). > > It does not generate conflicts because of the way REV1 is chosen, > and because of the way PATH1 and PATH2 are chosen. In fact, this must imply that you *can* get conflicts if any of the changes on trunk after rX conflicts with the "feature". But the recommended work flow would be to do the last "catch-up" (which defines X) just before the re-integrate, so the opportunity for such conflicts would be small. - Julian
