git rebase --onto never gets past rewinding head

Question

I have the following branches:

 ─┬──────────────────────────────────────┬──  master
  │                                      │
  │                                      │
  │                                      └── staging
  │
  │
  └─X───Y─┬─────────────────────────────────  develop
          │                         ▲
          │                         │
          └────A────────B──────C────┴──┬────  feature/abc
                                       │
                                       │
                                       └────  merge/feature/abc

Quick explanation of each one:

master: this is the production branch - anything merged here goes to production.
staging: this branch is used to temporarily group a bunch of different features that will go to production together as a release. Before a release, a fresh staging is cut from master.
develop: mainline branch - regular branch that features are continually integrated into, as they are completed.
feature/abc: a typical feature branch, cut from develop.
merge/feature/abc: a working branch that I am trying to rebase, so that I can prepare the feature to be rebased off staging, as I prepare to do a release. (I just don't want to mess up the feature/abc.)

I want to make the merge/feature/abc rebased off staging, so that it contains only the relevant commits in feature/abc. i.e. I want merge/feature/abc to contain only commits A, B, and C, but not X and Y. This would happen after the feature/abc branch has been merged and tested on develop.

According to the git manual, the commands I want is:

git rebase --onto staging develop merge/feature/abc

When I do that, the output says:

First, rewinding head to replay your work on top of it...

... and that's it - no other output. It just stops. As I understand it, there's supposed to be more output as git rebase applies commits. The merge/feature/abc branch does get rebased, but it does *not contain any commits from feature/abc, if I do git log. If I run git status, it says:

On branch merge/feature/abc
nothing to commit, working tree clean

If I run git diff staging, there is no diff. So it's basically reset to staging.

What am I doing wrong?

user_1256452 · Answer

This command:

git rebase --onto staging develop merge/feature/abc

is short for:

git checkout merge/feature/abc
git rebase --onto staging develop

Here develop is the upstream argument, which should disable fork-point mode. If for some reason it does not disable fork-point mode, adding --no-fork-point might help, but in any case, you might wish to run:

git log develop..merge/feature/abc

to see which commits would be candidates for copying here. If the list is empty, that's the answer right away: there are no candidate commits to be copied. If the list isn't empty, the next step is to examine these candidate commits:

Any merge commits will be omitted. Are the listed commits all merges? If so, they will all be omitted.
Any commits whose patch ID matches one in the upstream will be omitted.

This second point is what TTT is alluding to in this comment:

... (or their equivalents) ...

Finding patch-ID-equivalent commands is a bit trickier. The --left-right --cherry-mark options to git log / git rev-list, and the git cherry command, can do this. When using --cherry-mark with git log or git rev-list, it's necessary to use the three-dot symmetric difference operator:

git log --left-right --cherry-mark --oneline develop...merge/feature/abc

The cherry-mark option makes git log (or git rev-list) run each commit through the patch-ID generator and then marks equivalent commits with = instead of < or >. If there are commits listed by git log develop..merge/feature/abc, they would be right-hand-side > commits in this output; if they become marked with =, they're already in develop (or more precisely, Git thinks they are) so git rebase does not copy them.

If this is the issue, the --reapply-cherry-picks flag can help. This flag is relatively new, having first appeared in Git 2.27.0.

Note: a command for listing everything all at once, with merge commits omitted without you having to do anything, is:

git rev-list --left-right --cherry-mark --no-merges develop...merge/feature/abc

Only commits marked > would be copied. (Consider using git log --oneline for this as well, since that shows subject lines.)

git rebase --onto never gets past rewinding head

1 Answers