jj abandons commits and rebases descendants leaving conflicts

[tekumara]

On jj git fetch, 2 commits where abandoned (because the trunk-based branch has been merged and deleted on the remote). The descendants were rebased, leaving them in a conflicted state.

I'm trying to understand why jj wouldn't instead either:

1. keep the commits, since they have descendants
2. abandon the descendants too

Thank you!

❯ jj
Hint: Use `jj -h` for a list of available commands.
Run `jj config set --user ui.default-command log` to disable this message.
@  vunl [email protected] 2025-09-28 10:55:32 b349
│  (empty) (no description set)
○  mmnx [email protected] 2025-09-28 10:55:32 git_head() 35c4
│  rm .coverage
│ ○  yrop [email protected] 2025-09-28 10:37:22 15e7
├─╯  (no description set)
│ ○  klmk [email protected] 2025-09-24 14:39:02 4726
│ │  Skip bedrock tests in CI
│ ○  zwop [email protected] 2025-09-24 14:26:50 099a
│ │  Isort fix
│ ○  nlvw [email protected] 2025-09-24 14:25:13 9049
│ │  Isort fix
│ ○  nxtm [email protected] 2025-09-24 14:20:46 2e08
│ │  try known-third-party
│ ○  kqxr [email protected] 2025-09-24 13:52:00 8e79
│ │  sort import trial
│ ○  zuxl [email protected] 2025-09-24 13:50:25 99c0
│ │  unsort
│ ○  snvx [email protected] 2025-09-24 08:20:56 61de
│ │  Adjust pyright to exclude node_modules
│ ○  oumk [email protected] 2025-09-24 07:43:54 fbde
╭─┤  (empty) chore: cruft update (#247)
○ │  pyrn [email protected] 2025-09-23 22:22:16 103d
│ │  ruff
○ │  uwys [email protected] 2025-09-23 21:57:10 80da
├─╯  cruft update
○  wxko [email protected] 2025-09-23 21:44:54 trunk-based ca33
│  update contributing
○  rpxp [email protected] 2025-09-23 20:25:41 23e5
│  require pytest-mock
○  npvu [email protected] 2025-09-23 20:10:27 del-me ffb2

❯ jj git fetch
remote: Enumerating objects: 1, done.
remote: Total 1 (delta 0), reused 0 (delta 0), pack-reused 0 (from 0)
bookmark: main@origin        [updated] tracked
bookmark: trunk-based@origin [deleted] untracked
Abandoned 2 commits that are no longer reachable.
Rebased 13 descendant commits
Working copy  (@) now at: vunl 7201 (conflict) (empty) (no description set)
Parent commit (@-)      : mmnx e0d9 (conflict) rm .coverage
Added 0 files, modified 2 files, removed 0 files
Warning: There are unresolved conflicts at these paths:
pyproject.toml    2-sided conflict
New conflicts appeared in 11 commits:
  mmnx e0d9 (conflict) rm .coverage
  yrop 34e2 (conflict) (no description set)
  klmk 71cb (conflict) Skip bedrock tests in CI
  zwop 4c84 (conflict) Isort fix
  nlvw 2b38 (conflict) Isort fix
  nxtm 6fd5 (conflict) try known-third-party
  kqxr e0a4 (conflict) sort import trial
  zuxl 3c78 (conflict) unsort
  snvx 1f14 (conflict) Adjust pyright to exclude node_modules
  pyrn e07b (conflict) ruff
  ...
Hint: To resolve the conflicts, start by creating a commit on top of
the first conflicted commit:
  jj new uwys
Then use `jj resolve`, or edit the conflict markers in the file directly.
Once the conflicts are resolved, you can inspect the result with `jj diff`.
Then run `jj squash` to move the resolution into the conflicted commit.

❯ jj
Hint: Use `jj -h` for a list of available commands.
Run `jj config set --user ui.default-command log` to disable this message.
@  vunl [email protected] 2025-09-29 10:16:29 7201 conflict
│  (empty) (no description set)
×  mmnx [email protected] 2025-09-29 10:16:29 git_head() e0d9 conflict
│  rm .coverage
│ ×  yrop [email protected] 2025-09-29 10:16:29 34e2 conflict
├─╯  (no description set)
│ ×  klmk [email protected] 2025-09-29 10:16:29 71cb conflict
│ │  Skip bedrock tests in CI
│ ×  zwop [email protected] 2025-09-29 10:16:29 4c84 conflict
│ │  Isort fix
│ ×  nlvw [email protected] 2025-09-29 10:16:29 2b38 conflict
│ │  Isort fix
│ ×  nxtm [email protected] 2025-09-29 10:16:29 6fd5 conflict
│ │  try known-third-party
│ ×  kqxr [email protected] 2025-09-29 10:16:29 e0a4 conflict
│ │  sort import trial
│ ×  zuxl [email protected] 2025-09-29 10:16:29 3c78 conflict
│ │  unsort
│ ×  snvx [email protected] 2025-09-29 10:16:29 1f14 conflict
│ │  Adjust pyright to exclude node_modules
│ ×  oumk [email protected] 2025-09-29 10:16:29 fbed conflict
╭─┤  (empty) chore: cruft update (#247)
× │  pyrn [email protected] 2025-09-29 10:16:29 e07b conflict
│ │  ruff
× │  uwys [email protected] 2025-09-29 10:16:29 f1fe conflict
├─╯  cruft update
○  npvu [email protected] 2025-09-23 20:10:27 del-me ffb2
│  .

[jennings]

It's expected that your next step is to rebase the branch onto trunk() (or wherever the abandoned commits landed). Doing so will resolve the conflicts.

jj rebase -d main -b klmk

# since the branch contains @, and -b @ 
# is the default rebase source, you
# could simplify it to this:
jj rebase -d main

We'd like to have a jj git sync that does this fetch-then-rebase automatically but it's nontrivial and needs design.

The justification for this behavior is that jj is trying to keep the repo in sync with git. In git, deleting the remote branch makes the commits from that branch unreachable. The equivalent operation in jj is to abandon them. Since your anonymous commits were not reachable from git in the first place, they are not abandoned.

[tekumara]

Thank you @jennings.

Since your anonymous commits were not reachable from git in the first place, they are not abandoned.

Got it, this makes sense. What actually happened here is the remote trunk-based branch was moved backwards to wxko which left its descendant commits existing only in the local repository.