Add e2e case for missing worktree after crash

main.go

@@ -1681,6 +1681,9 @@ func (git *repoSync) SyncRepo(ctx context.Context, refreshCreds func(context.Con
 		// Regular cleanup will happen in the outer loop, to catch stale
 		// worktrees.
 
+		// We can end up here with no current hash but (the expectation of) a
+		// current worktree (e.g. the hash was synced but the worktree does not
+		// exist).
 		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.

test_e2e.sh

@@ -1297,7 +1297,7 @@ function e2e::sync_sha_once_sync_different_sha_unknown() {
 ##############################################
 # Test syncing after a crash
 ##############################################
-function e2e::sync_crash_cleanup_retry() {
+function e2e::sync_crash_no_link_cleanup_retry() {
     # First sync
     echo "$FUNCNAME 1" > "$REPO/file"
     git -C "$REPO" commit -qam "$FUNCNAME 1"
@@ -1325,6 +1325,37 @@ function e2e::sync_crash_cleanup_retry() {
     assert_file_eq "$ROOT/link/file" "$FUNCNAME 1"
 }
 
+##############################################
+# Test syncing after a crash
+##############################################
+function e2e::sync_crash_no_worktree_cleanup_retry() {
+    # First sync
+    echo "$FUNCNAME 1" > "$REPO/file"
+    git -C "$REPO" commit -qam "$FUNCNAME 1"
+
+    GIT_SYNC \
+        --one-time \
+        --repo="file://$REPO" \
+        --root="$ROOT" \
+        --link="link"
+    assert_link_exists "$ROOT/link"
+    assert_file_exists "$ROOT/link/file"
+    assert_file_eq "$ROOT/link/file" "$FUNCNAME 1"
+
+    # Corrupt it
+    rm -rf "$ROOT/.worktrees/"
+
+    # Try again
+    GIT_SYNC \
+        --one-time \
+        --repo="file://$REPO" \
+        --root="$ROOT" \
+        --link="link"
+    assert_link_exists "$ROOT/link"
+    assert_file_exists "$ROOT/link/file"
+    assert_file_eq "$ROOT/link/file" "$FUNCNAME 1"
+}
+
 ##############################################
 # Test changing repos with storage intact
 ##############################################