Can you share your rationale as to why this is incorrect? It seems to mesh well with the text that comes just before it (emphasis mine):

If you have a more important project, you might want to use a two-phase merge cycle. In this scenario, you have two long-running branches, master and develop, in which you determine that master is updated only when a very stable release is cut and all new code is integrated into the develop branch. You regularly push both of these branches to the public repository. Each time you have a new topic branch to merge in (Figure 5-22), you merge it into develop (Figure 5-23); then, when you tag a release, you fast-forward master to wherever the now-stable develop branch is (Figure 5-24).

"Is it acceptable that the caption and the alt text for an image are different?" was what I was thinking when I made this pull request. Like you said, the original phrase makes perfect sense. I chose to stick to the first edition as I was not sure whether the caption and the alt text were differed intentionally.

Listed are what we can do:

1. close this pull request and leave this part of the section as is
2. keep the original phrase and update the alt text to "After a project release"
3. merge this pull request

Option 2 is the right way to go, I suppose? And if so, is it OK to add another commit to this pull request for that?

Sorry for the confusing commit messege, it should've been something like "Make the caption and the alt text same".

Ah, I see what the problem is now. Yes, please continue with option 2; replace the alt-text with the figure caption text. I'll leave it up to you whether it comes in as one commit or two. Thanks for this!