fix: infinite bad loop caused by unexpected worktree directory removal

main.go

@@ -2038,7 +2038,7 @@ func (git *repoSync) SyncRepo(ctx context.Context, refreshCreds func(context.Con
 		// Regular cleanup will happen in the outer loop, to catch stale
 		// worktrees.
 
-		if currentWorktree != git.worktreeFor(currentHash) {
+		if currentHash != "" && currentWorktree != git.worktreeFor(currentHash) {
 			// The old worktree might have come from a prior version, and so
 			// not get caught by the normal cleanup.
 			os.RemoveAll(currentWorktree.Path().String())

test_e2e.sh

@@ -608,6 +608,51 @@ function e2e::worktree_cleanup() {
     assert_file_absent "$ROOT/.worktrees/not_a_directory"
 }
 
+##############################################
+# Test worktree-unexpected-removal
+##############################################
+function e2e::worktree_unexpected_removal() {
+    GIT_SYNC \
+        --period=100ms \
+        --repo="file://$REPO" \
+        --root="$ROOT" \
+        --link="link" \
+        &
+
+    # wait for first sync
+    wait_for_sync "${MAXWAIT}"
+    assert_link_exists "$ROOT/link"
+    assert_file_exists "$ROOT/link/file"
+    assert_file_eq "$ROOT/link/file" "$FUNCNAME"
+    assert_metric_eq "${METRIC_GOOD_SYNC_COUNT}" 1
+    assert_metric_eq "${METRIC_FETCH_COUNT}" 1
+
+    # suspend time so we can fake corruption
+    docker ps --filter label="git-sync-e2e=$RUNID" --format="{{.ID}}" \
+        | while read CTR; do
+            docker pause "$CTR" >/dev/null
+        done
+
+    # make a unexpected removal
+    WT=$(git -C "$REPO" rev-list -n1 HEAD)
+    rm -r "$ROOT/.worktrees/$WT"    
+
+    # resume time
+    docker ps --filter label="git-sync-e2e=$RUNID" --format="{{.ID}}" \
+        | while read CTR; do
+            docker unpause "$CTR" >/dev/null
+        done
+
+    echo "$METRIC_GOOD_SYNC_COUNT"
+
+    wait_for_sync "${MAXWAIT}"
+    assert_link_exists "$ROOT/link"
+    assert_file_exists "$ROOT/link/file"
+    assert_file_eq "$ROOT/link/file" "$FUNCNAME"
+    assert_metric_eq "${METRIC_GOOD_SYNC_COUNT}" 2
+    assert_metric_eq "${METRIC_FETCH_COUNT}" 2
+}
+
 ##############################################
 # Test stale-worktree-timeout
 ##############################################