cli+tui: make repeated but undos work

[davidpdrsn]

Previously, if you ran but undo and then but undo again, you'd undo the undo. Thats not intended and instead, what we want to do is undo the operation before the previous undo, basically walking backwards in history. This makes but undo do that.

How it works

I find the undo target by walking from newest to oldest through the oplog and counting how many undos we see. For each undo we see, we skip one non-undo entry. When we're at 0, we know the target is the next entry.

Example when all undos are at the top

                                    (n=0)
[UNDO]   <- skip one real operation (n=1)
[UNDO]   <- skip one real operation (n=2)
[REWORD] <- skipped                 (n=1)
[REWORD] <- skipped                 (n=0)
[REWORD] <- target                  take this!

And with undos mixed with other operations

                                         (n=0)
[UNDO]   <- skip one real operation      (n=1)
[REWORD] <- skipped                      (n=0)
[UNDO]   <- skip one more real operation (n=1)
[REWORD] <- skipped                      (n=0)
[REWORD] <- target                       take this!

Undoing but oplog restore

I want but oplog restore to be treated differently from but undo, i.e., if you run but oplog restore and then but undo, then we should undo the restore. The restore shouldn't be counted as an undo.

This required changing OperationKind, which previously used RestoreFromSnapshot for both undos and restores. I've added a new RestoreFromSnapshotViaUndo variant that is used for undos so we can tell them apart from explicit restores. That means old undo entries will be categorized as restores, but I don't think there is anything we can do about that.

but redo

We also want to add but redo to walk forwards in the oplog. I'm pretty confident we can use the same general strategy to support that as well, but if someone disagrees, I'd like to know 😊 since this introduces data changes. I want to make sure we don't need to make further changes when we do but redo. I might wait to merge this until I have a working but redo implementation as well.

Iterating the oplog

Before, we had ctx.list_snapshots(), which returned a Vec<Snapshot> and required passing a limit on how many oplog entries to retrieve. I've changed that to instead be ctx.snapshots_iter(), which returns a lazy iterator. We need this because we don't know specifically how far to walk back to find the undo target, so we cannot provide a limit upfront.

One small behavior change here is that when iterating from a specific oplog commit, that commit isn't included, whereas before it would be. I think this behavior is more appropriate for pagination since clients can just pass the last commit and get exactly the next page to render. There was even a TODO about that in the Svelte app.

GUI changes

The new OperationKind did require some changes in Svelte land, which I'm really not familiar with, so I would like some extra eyes on that.

[Copilot]

Pull request overview

This PR updates the oplog/undo plumbing so repeated but undo walks further back in history (instead of undoing the previous undo), and introduces a lazy snapshot iterator to support traversing the oplog without a pre-known limit. It also attempts to distinguish “undo restores” from explicit but oplog restore operations via new restore/oplog kinds.

Changes:

• Added lazy snapshot traversal (snapshots_iter) and updated callers/tests away from list_snapshots(limit, ...).
• Added RestoreKind / new OperationKind variants and wired them through restore APIs.
• Added undo-target selection logic (get_undo_target_snapshot) and new CLI tests for repeated undo.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
crates/gitbutler-oplog/src/oplog.rs	Replaces eager snapshot listing with an iterator; adds RestoreKind; updates restore snapshot recording.
crates/gitbutler-oplog/src/lib.rs	Re-exports RestoreKind.
crates/gitbutler-oplog/src/entry.rs	Splits restore operation kinds and adds backward-compatible parsing for legacy trailer values.
crates/gitbutler-branch-actions/tests/branch-actions/virtual_branches/oplog.rs	Migrates tests from list_snapshots to snapshots_iter and updates restore signature.
crates/but/tests/but/command/undo.rs	Adds CLI tests for repeated undo and explicit restore undo behavior.
crates/but/src/command/legacy/status/tui/mod.rs	Switches undo flow to get_undo_target_snapshot and passes restore kind.
crates/but/src/command/legacy/rub/squash.rs	Updates restore signature on squash rollback path.
crates/but/src/command/legacy/oplog.rs	Migrates oplog list to iterator; switches undo to get_undo_target_snapshot; updates restore API calls.
crates/but-api/src/legacy/oplog.rs	Implements iterator wrapper + undo-target logic; introduces API-level RestoreKind; updates restore API signature.

[Copilot]

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Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

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[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

[Copilot]

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[mtsgrd]

lgtm

[Copilot]

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