What is "concurrent checkout" and how can it occur?

[BatmanAoD]

I got this error:

Internal error: Failed to check out commit 57b7b31bbf4a6ad0ff610cf5b761c4c289c50d71
Caused by: Concurrent checkout

The repo is actually quite new, and I only have one workspace, so I've attached the entire op log. It looks like maybe a single git fetch turned into two concurrent operations with a race.

jj-concurrent-checkout.log

[martinvonz]

Copying the relevant part of the operation log to here for reference:

○    3172f4886d6b kstrand@RM-LOSX-0F2WP14 2 minutes ago, lasted 5 milliseconds
├─╮  reconcile divergent operations
│ │  args: jj operation log --limit 1 -T 'self.id()' --no-graph --config-file /Users/kstrand/.vscode/extensions/jjk.jjk-0.8.1/dist/config.toml
○ │  b0997b11c2a6 kstrand@RM-LOSX-0F2WP14 2 minutes ago, lasted 8 milliseconds
│ │  import git refs
│ │  args: jj operation log --limit 1 -T 'self.id()' --no-graph --config-file /Users/kstrand/.vscode/extensions/jjk.jjk-0.8.1/dist/config.toml
│ ○  c41b70ed742d kstrand@RM-LOSX-0F2WP14 2 minutes ago, lasted 1 second
├─╯  fetch from git remote(s) origin
│    args: jj git fetch
○  36f6e43fd874 kstrand@RM-LOSX-0F2WP14 7 minutes ago, lasted 1 second
│  push bookmark chore-first-release to git remote origin
│  args: jj git push

So it doesn't look like a single jj git fetch creating two operation, it looks like one jj git fetch and one jj operation log --limit 1 -T 'self.id()' --no-graph --config-file /Users/kstrand/.vscode/extensions/jjk.jjk-0.8.1/dist/config.toml call. I think has the same root cause as #6830.

[BatmanAoD]

Aha, I had forgotten that I installed a jj extension for VSCode. I think for now I'll probably just uninstall it again.