feat: skip checkpoints when worktree unchanged (read-only bash like ls, find, cat)

Compares worktreeTreeSha after creating checkpoint — if identical to last
checkpoint, deletes it immediately. Eliminates false positives from read-only
bash commands during planning/exploration turns.

Before: every bash tool triggered a checkpoint (even ls, cat, grep)
After: only checkpoints when files actually change

Author: arpagon

package.json

@@ -1,6 +1,6 @@
 {
   "name": "pi-rewind",
-  "version": "0.3.1",
+  "version": "0.3.2",
   "description": "Checkpoint/rewind extension for the Pi coding agent — per-tool snapshots, /rewind command, Esc+Esc shortcut, safe restore, redo stack",
   "license": "MIT",
   "author": "arpagon",

src/index.ts

@@ -20,6 +20,7 @@ import {
   isGitRepo,
   getRepoRoot,
   createCheckpoint,
+  deleteCheckpoint,
   loadAllCheckpoints,
   pruneCheckpoints,
   MUTATING_TOOLS,
@@ -97,6 +98,7 @@ export default function (pi: ExtensionAPI) {
       });
       state.resumeCheckpoint = cp;
       state.checkpoints.set(cp.id, cp);
+      state.lastWorktreeTree = cp.worktreeTreeSha;
     } catch {
       // Resume checkpoint is optional
     }
@@ -196,7 +198,15 @@ export default function (pi: ExtensionAPI) {
             turnIndex: state.currentTurnIndex,
             description: desc,
           });
+
+          // Skip if worktree is identical to last checkpoint (read-only bash like ls, find, cat)
+          if (state.lastWorktreeTree && cp.worktreeTreeSha === state.lastWorktreeTree) {
+            await deleteCheckpoint(state.repoRoot!, cp.id);
+            return;
+          }
+
           state.checkpoints.set(cp.id, cp);
+          state.lastWorktreeTree = cp.worktreeTreeSha;
           updateStatus(state, ctx);
         } catch {
           // Checkpoint failures are non-fatal

src/state.ts

@@ -33,6 +33,8 @@ export interface RewindState {
   turnToolDescriptions: string[];
   /** Whether the current turn had any mutating tool calls */
   turnHadMutations: boolean;
+  /** Last worktree tree SHA (to detect actual file changes) */
+  lastWorktreeTree: string | null;
 }
 
 export function createInitialState(): RewindState {
@@ -50,6 +52,7 @@ export function createInitialState(): RewindState {
     pendingToolInfo: new Map(),
     turnToolDescriptions: [],
     turnHadMutations: false,
+    lastWorktreeTree: null,
   };
 }
 
@@ -67,4 +70,5 @@ export function resetState(state: RewindState): void {
   state.pendingToolInfo.clear();
   state.turnToolDescriptions = [];
   state.turnHadMutations = false;
+  state.lastWorktreeTree = null;
 }