> But there isn't a way to view the "interdiff" between the version of the branch before review and the version of the branch after review. Review tools like Phabricator, Gerrit, and email lists allow one do view that diff.
Yes there is. You even get a link to view that exact diff whenever someone updates a PR. It shows changes since you last viewed the PR, up to its current state.
That's only the case if someone pushes up a commit like "Addressing comments" or "Fixed bug". If you rebase locally and force push the branch to maintain the clean set of commits after addressing review comments, Github does not provide a way to see the diff between the previous branch head commit and the current head commit.
> If you rebase locally and force push the branch to maintain the clean set of commits after addressing review comments
Why would you do that, in general? That seems needlessly hostile to reviewers, since then they have to go through your diff and make sure you caught every place their comment applied (e.g. "did they actually handle the else-case everywhere they're testing on $var?").
Is this common practice in situations* where it harms diff readability? If so, why?
* There are totally cases where that's necessary, but they don't seem like more than a small minority of comment/feedback/amendment cases. These are times like "you put all of this code in the totally wrong place" or "this is missing a fundamental assumption that would require you to totally rearchitect every change you wrote". In those cases, a rebase (plus clearly calling out "everything was rebased starting here please start reading from here on!") or a brand new branch is in order.
The main purpose is to maintain a clean set of commits. So rather than having a history like:
Add method and unit tests
Update version to 1.2.3
Fixed issue in method
Fixed syntax error
Addressing review comments
you only have the first two commits.
> That seems needlessly hostile to reviewers
Why would doing something like this be considered hostile? The problem here is the tool used for reviewing code, not the submitter or reviewers. Other review tools have had the feature of viewing the diff of the branch across rebases for quite some time now.
The only other alternative is to rely on the submitter to make sure they squash the amendments they make into the correct commit. That in itself is more difficult after making multiple commits of that nature. What usually happens in that case is that those commits end up as part of the master branch. This makes it more difficult to revert certain changes because they're split across multiple commits and it also makes it more difficult to track down the source of a bug. It also makes it more difficult to see which commit was responsible for a given change when using git blame.
The problem I run into when reviewing PRs on Github is that many people rebase or otherwise mutate their history locally to address review comments, then force push to the branch being reviewed. Once they've done that, you've lost the original commits and can't see how the new ones differ.
I dislike when questions are worded like that, because it could be interpreted in two ways:
a) Given an arbitrary case, is there a chance that modifying commits is considered a poor practise in that case?
b) Is the belief that modifying commits is poor practise held by the population at large?
The answer to a) is yes, the answer to b) is no.
Some people prefer a clean history, where you have to explicitly request the steps to get to it if you want them. Others want the messy steps to be part of the history you show up-front.
Yes there is. You even get a link to view that exact diff whenever someone updates a PR. It shows changes since you last viewed the PR, up to its current state.