March 2018 | Page 2 of 3 | The Old New Thing

The mystery of the stalker dental hygienist

Raymond ChenMarch 22, 2018Mar 22, 201803/22/18

Ony of my colleagues remarked that every time he visits the dentist, the hygienist seems to have stalker-level knowledge of his life. "How did your son do at the chess tournament?" "Have you decided to do anything fun with your brother's family when they come to visit?" "Did your wife's performance go well?" Eventually, he realized why the...

Stop cherry-picking, start merging, Part 9: Chasing the commit

Raymond ChenMarch 22, 2018Mar 22, 201803/22/18

Consider the following situation: From a starting common commit A (where the line is "apple"), the master branch makes an unrelated commit M1. Meanwhile we branch off from commit A with a new branch called "victim", on which unrelated commits V1 and V2 are made. From commit V1, another branch called "feature...

Stop cherry-picking, start merging, Part 8: How to merge a partial cherry-pick

Raymond ChenMarch 21, 2018Mar 21, 201803/21/18

Continuing our exploration of using merges as a replacement for cherry-picking, here's another scenario you can now solve: What if I want to take only part of a commit into another branch? Well, if you haven't committed the change yet, then you can follow the usual workflow: Create a patch branch, commit only the part that you want to go ...

Stop cherry-picking, start merging, Part 7: Preventing a change from leaving a branch

Raymond ChenMarch 20, 2018Mar 20, 201803/20/18

Still continuing our exploration of using merges as a replacement for cherry-picking, here's another scenario you can now solve: How do I make a change in a branch that will not propagate when it merges? Suppose you have a develop branch where active development occurs, and you also have a release branch that represents the current release ...

Stop cherry-picking, start merging, Part 6: Replacing the temporary fix with the permanent fix

Raymond ChenMarch 19, 2018Mar 19, 201803/19/18

Continuing our exploration of using merges as a replacement for cherry-picking, here's another scenario you can now solve: How do I make a change in the master branch that will be automatically reverted when the feature branch merges in? For this scenario, you have a starting commit A from which you create a feature branch. Both the master ...

Stop cherry-picking, start merging, Part 5: Exploiting the three-way merge

Raymond ChenMarch 16, 2018Mar 16, 201803/16/18

Last time, we answered some questions based on what we know about the recursive merge algorithm. Today, we'll answer questions based on what we know about the three-way merge algorithm. After choosing a merge base (possibly by manufacturing one via the recursive merge algorithm), the three-way merge algorithm takes the three versions ...

Stop cherry-picking, start merging, Part 4: Exploiting the recursive merge algorithm

Raymond ChenMarch 15, 2018Mar 15, 201803/15/18

The last few days have looked at the dangers of cherry-picking, both in terms of latent merge conflicts and (even worse) missing merge conflicts, and last time, I proposed the alternative to cherry-picking: Merging from a common branch. Before we can explore further, we need to understand the recursive merge algorithm. Instead of trying to ...

Stop cherry-picking, start merging, Part 3: Avoiding problems by creating a new merge base

Raymond ChenMarch 14, 2018Mar 14, 201803/14/18

The first two parts of the series discussed the bad things that can happen if you cherry-pick a change that is subsequently modified. If you're lucky, you get a merge conflict. If you're not lucky, your modification is simply ignored. If only there were a way to do a partial merge instead of a cherry-pick, the problems could have been avoided...

Stop cherry-picking, start merging, Part 2: The merge conflict that never happened (but should have)

Raymond ChenMarch 13, 2018Mar 13, 201803/13/18

Last time, we saw how editing the code affected by a cherry-pick creates a potential merge conflict that doesn't become realized until the original commit and its cherry-picked doppelgänger meet in a merge somewhere, which could be far away from the branches that contained the original commit and its cherry-pick. But you know what's ...

Stop cherry-picking, start merging, Part 1: The merge conflict

Raymond ChenMarch 12, 2018Mar 12, 201803/12/18

Setting the pieces into motion.

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