From a76417e9a241128b1e6c0395129bd687a1c8ef22 Mon Sep 17 00:00:00 2001
From: "John T. Wodder II" <git@varonathe.org>
Date: Thu, 6 May 2021 11:30:32 -0400
Subject: [PATCH 1/4] Add "sync" upload option

---
 dandi/cli/cmd_upload.py    |  5 +++++
 dandi/tests/fixtures.py    |  4 ++--
 dandi/tests/test_upload.py | 35 +++++++++++++++++++++++++++++++++++
 dandi/upload.py            | 25 +++++++++++++++++++++++++
 4 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/dandi/cli/cmd_upload.py b/dandi/cli/cmd_upload.py
index 1632922c1..27e468b73 100644
--- a/dandi/cli/cmd_upload.py
+++ b/dandi/cli/cmd_upload.py
@@ -50,6 +50,9 @@ def get_metavar(self, param):
     type=IntColonInt(),
     help="Number of files to upload in parallel and, optionally, number of upload threads per file",
 )
+@click.option(
+    "--sync", is_flag=True, help="Delete assets on the server that do not exist locally"
+)
 @click.option(
     "--validation",
     help="Data must pass validation before the upload.  Use of this option is highly discouraged.",
@@ -80,6 +83,7 @@ def get_metavar(self, param):
 def upload(
     paths,
     jobs,
+    sync,
     existing="refresh",
     validation="require",
     dandiset_path=None,
@@ -121,4 +125,5 @@ def upload(
         devel_debug=devel_debug,
         jobs=jobs,
         jobs_per_file=jobs_per_file,
+        sync=sync,
     )
diff --git a/dandi/tests/fixtures.py b/dandi/tests/fixtures.py
index 7eab60369..6069db822 100644
--- a/dandi/tests/fixtures.py
+++ b/dandi/tests/fixtures.py
@@ -284,11 +284,11 @@ def text_dandiset(local_dandi_api, monkeypatch, tmp_path_factory):
     (dspath / "subdir2" / "banana.txt").write_text("Banana\n")
     (dspath / "subdir2" / "coconut.txt").write_text("Coconut\n")
 
-    def upload_dandiset(**kwargs):
+    def upload_dandiset(paths=None, **kwargs):
         with monkeypatch.context() as m:
             m.setenv("DANDI_API_KEY", local_dandi_api["api_key"])
             upload(
-                paths=[],
+                paths=paths or [],
                 dandiset_path=dspath,
                 dandi_instance=local_dandi_api["instance_id"],
                 devel_debug=True,
diff --git a/dandi/tests/test_upload.py b/dandi/tests/test_upload.py
index 1de9fe3b5..d53d9ab84 100644
--- a/dandi/tests/test_upload.py
+++ b/dandi/tests/test_upload.py
@@ -151,3 +151,38 @@ def test_upload_download_small_file(contents, local_dandi_api, monkeypatch, tmp_
         download_dir / dandiset_id / "file.txt",
     ]
     assert files[1].read_bytes() == contents
+
+
+@pytest.mark.parametrize("confirm", [True, False])
+def test_upload_sync(confirm, mocker, text_dandiset):
+    (text_dandiset["dspath"] / "file.txt").unlink()
+    confirm_mock = mocker.patch("click.confirm", return_value=confirm)
+    text_dandiset["reupload"](sync=True)
+    confirm_mock.assert_called_with("Delete 1 assets on server?")
+    asset = text_dandiset["client"].get_asset_bypath(
+        text_dandiset["dandiset_id"], "draft", "file.txt"
+    )
+    if confirm:
+        assert asset is None
+    else:
+        assert asset is not None
+
+
+def test_upload_sync_folder(mocker, text_dandiset):
+    (text_dandiset["dspath"] / "file.txt").unlink()
+    (text_dandiset["dspath"] / "subdir2" / "banana.txt").unlink()
+    confirm_mock = mocker.patch("click.confirm", return_value=True)
+    text_dandiset["reupload"](paths=[text_dandiset["dspath"] / "subdir2"], sync=True)
+    confirm_mock.assert_called_with("Delete 1 assets on server?")
+    assert (
+        text_dandiset["client"].get_asset_bypath(
+            text_dandiset["dandiset_id"], "draft", "file.txt"
+        )
+        is not None
+    )
+    assert (
+        text_dandiset["client"].get_asset_bypath(
+            text_dandiset["dandiset_id"], "draft", "subdir2/banana.txt"
+        )
+        is None
+    )
diff --git a/dandi/upload.py b/dandi/upload.py
index 5adba8da2..8695f5a46 100644
--- a/dandi/upload.py
+++ b/dandi/upload.py
@@ -1,7 +1,11 @@
+from functools import reduce
+import os.path
 from pathlib import Path, PurePosixPath
 import re
 import time
 
+import click
+
 from .consts import dandiset_identifier_regex, dandiset_metadata_file
 from . import lgr
 from .utils import ensure_datetime, get_instance
@@ -18,6 +22,7 @@ def upload(
     devel_debug=False,
     jobs=None,
     jobs_per_file=None,
+    sync=False,
 ):
     from .dandiapi import DandiAPIClient
     from .dandiset import APIDandiset, Dandiset
@@ -61,6 +66,7 @@ def upload(
     #
     if not paths:
         paths = [dandiset.path]
+    original_paths = paths
 
     # Expand and validate all paths -- they should reside within dandiset
     paths = find_files(".*", paths) if allow_any_path else find_dandi_files(paths)
@@ -335,3 +341,22 @@ def upload_agg(*ignored):
                 else:
                     rec.update(skip_file(exc))
             out(rec)
+
+    if sync:
+        relpaths = []
+        for p in original_paths:
+            rp = os.path.relpath(p, dandiset.path)
+            relpaths.append("" if rp == "." else rp)
+        path_prefix = reduce(os.path.commonprefix, relpaths)
+        to_delete = []
+        for asset in client.get_dandiset_assets(
+            ds_identifier, "draft", path=path_prefix
+        ):
+            if (
+                any(p == "" or path_is_subpath(asset["path"], p) for p in relpaths)
+                and not Path(dandiset.path, asset["path"]).exists()
+            ):
+                to_delete.append(asset["asset_id"])
+        if to_delete and click.confirm(f"Delete {len(to_delete)} assets on server?"):
+            for asset_id in to_delete:
+                client.delete_asset(ds_identifier, "draft", asset_id)

From fcea4034699d73836e18acb77976f795273a7b16 Mon Sep 17 00:00:00 2001
From: "John T. Wodder II" <git@varonathe.org>
Date: Fri, 7 May 2021 11:31:33 -0400
Subject: [PATCH 2/4] Add "sync" download option

---
 dandi/cli/cmd_download.py        |  6 ++-
 dandi/cli/tests/test_download.py |  7 +++
 dandi/download.py                | 87 ++++++++++++++++++++------------
 dandi/tests/test_download.py     | 40 +++++++++++++++
 4 files changed, 108 insertions(+), 32 deletions(-)

diff --git a/dandi/cli/cmd_download.py b/dandi/cli/cmd_download.py
index 67e8882c5..165994b52 100644
--- a/dandi/cli/cmd_download.py
+++ b/dandi/cli/cmd_download.py
@@ -73,6 +73,9 @@ def get_metavar(self, param):
     default="all",
     show_default=True,
 )
+@click.option(
+    "--sync", is_flag=True, help="Delete local assets that do not exist on the server"
+)
 @instance_option()
 # Might be a cool feature, not unlike verifying a checksum, we verify that
 # downloaded file passes the validator, and if not -- alert
@@ -91,7 +94,7 @@ def get_metavar(self, param):
 @click.argument("url", nargs=-1)
 @map_to_click_exceptions
 def download(
-    url, output_dir, existing, jobs, format, download_types, dandi_instance=None
+    url, output_dir, existing, jobs, format, download_types, sync, dandi_instance=None
 ):
     """Download a file or entire folder from DANDI"""
     # We need to import the download module rather than the download function
@@ -133,5 +136,6 @@ def download(
         jobs=jobs,
         get_metadata="dandiset.yaml" in download_types,
         get_assets="assets" in download_types,
+        sync=sync,
         # develop_debug=develop_debug
     )
diff --git a/dandi/cli/tests/test_download.py b/dandi/cli/tests/test_download.py
index 31a59cb8c..21ded7aa0 100644
--- a/dandi/cli/tests/test_download.py
+++ b/dandi/cli/tests/test_download.py
@@ -21,6 +21,7 @@ def test_download_defaults(mocker):
         jobs=6,
         get_metadata=True,
         get_assets=True,
+        sync=False,
     )
 
 
@@ -36,6 +37,7 @@ def test_download_all_types(mocker):
         jobs=6,
         get_metadata=True,
         get_assets=True,
+        sync=False,
     )
 
 
@@ -51,6 +53,7 @@ def test_download_metadata_only(mocker):
         jobs=6,
         get_metadata=True,
         get_assets=False,
+        sync=False,
     )
 
 
@@ -66,6 +69,7 @@ def test_download_assets_only(mocker):
         jobs=6,
         get_metadata=False,
         get_assets=True,
+        sync=False,
     )
 
 
@@ -96,6 +100,7 @@ def test_download_gui_instance_in_dandiset(mocker):
         jobs=6,
         get_metadata=True,
         get_assets=True,
+        sync=False,
     )
 
 
@@ -117,6 +122,7 @@ def test_download_api_instance_in_dandiset(mocker):
         jobs=6,
         get_metadata=True,
         get_assets=True,
+        sync=False,
     )
 
 
@@ -142,6 +148,7 @@ def test_download_url_instance_match(mocker):
         jobs=6,
         get_metadata=True,
         get_assets=True,
+        sync=False,
     )
 
 
diff --git a/dandi/download.py b/dandi/download.py
index 764b506ed..16d612953 100644
--- a/dandi/download.py
+++ b/dandi/download.py
@@ -8,6 +8,7 @@
 import sys
 import time
 
+import click
 import humanize
 import requests
 
@@ -16,7 +17,7 @@
 from .dandiset import Dandiset
 from . import get_logger
 from .support.pyout import naturalsize
-from .utils import ensure_datetime, flattened, is_same_time
+from .utils import ensure_datetime, find_files, flattened, is_same_time, on_windows
 
 lgr = get_logger()
 
@@ -30,12 +31,31 @@ def download(
     jobs=1,
     get_metadata=True,
     get_assets=True,
+    sync=False,
 ):
     # TODO: unduplicate with upload. For now stole from that one
     # We will again use pyout to provide a neat table summarizing our progress
     # with upload etc
     from .support import pyout as pyouts
 
+    urls = flattened([urls])
+    if len(urls) > 1:
+        raise NotImplementedError("multiple URLs not supported")
+    if not urls:
+        # if no paths provided etc, we will download dandiset path
+        # we are at, BUT since we are not git -- we do not even know
+        # on which instance it exists!  Thus ATM we would do nothing but crash
+        raise NotImplementedError("No URLs were provided.  Cannot download anything")
+
+    parsed_url = parse_dandi_url(urls[0])
+
+    # TODO: if we are ALREADY in a dandiset - we can validate that it is the
+    # same dandiset and use that dandiset path as the one to download under
+    if isinstance(parsed_url, DandisetURL):
+        output_path = op.join(output_dir, parsed_url.dandiset_id)
+    else:
+        output_path = output_dir
+
     # dandi.cli.formatters are used in cmd_ls to provide switchable
     pyout_style = pyouts.get_style(hide_if_missing=False)
 
@@ -56,8 +76,8 @@ def download(
         kw["yield_generator_for_fields"] = rec_fields[1:]  # all but path
 
     gen_ = download_generator(
-        urls,
-        output_dir,
+        parsed_url,
+        output_path,
         existing=existing,
         get_metadata=get_metadata,
         get_assets=get_assets,
@@ -81,10 +101,38 @@ def download(
     else:
         raise ValueError(format)
 
+    if sync and not isinstance(parsed_url, SingleAssetURL):
+        client = parsed_url.get_client()
+        with client.session():
+            asset_paths = {asset["path"] for asset in parsed_url.get_assets(client)}
+        if isinstance(parsed_url, DandisetURL):
+            prefix = os.curdir
+            download_dir = output_path
+        elif isinstance(parsed_url, MultiAssetURL):
+            folder_path = op.normpath(parsed_url.path)
+            prefix = folder_path
+            download_dir = op.join(output_path, op.basename(folder_path))
+        else:
+            raise NotImplementedError(
+                f"Unexpected URL type {type(parsed_url).__name__}"
+            )
+        to_delete = []
+        for p in find_files(".*", download_dir, exclude_datalad=True):
+            if p == op.join(output_path, dandiset_metadata_file):
+                continue
+            a_path = op.normpath(op.join(prefix, op.relpath(p, download_dir)))
+            if on_windows:
+                a_path = a_path.replace("\\", "/")
+            if a_path not in asset_paths:
+                to_delete.append(p)
+        if to_delete and click.confirm(f"Delete {len(to_delete)} local assets?"):
+            for p in to_delete:
+                os.unlink(p)
+
 
 def download_generator(
-    urls,
-    output_dir,
+    parsed_url,
+    output_path,
     *,
     assets_it=None,
     yield_generator_for_fields=None,
@@ -107,38 +155,15 @@ def download_generator(
       summary statistics while already downloading.  TODO: reimplement properly!
 
     """
-    urls = flattened([urls])
-    if len(urls) > 1:
-        raise NotImplementedError("multiple URLs not supported")
-    if not urls:
-        # if no paths provided etc, we will download dandiset path
-        # we are at, BUT since we are not git -- we do not even know
-        # on which instance it exists!  Thus ATM we would do nothing but crash
-        raise NotImplementedError("No URLs were provided.  Cannot download anything")
 
-    parsed_url = parse_dandi_url(urls[0])
     with parsed_url.navigate() as (client, dandiset, assets):
         if assets_it:
             assets_it.gen = assets
             assets = assets_it
 
-        # TODO: if we are ALREADY in a dandiset - we can validate that it is the
-        # same dandiset and use that dandiset path as the one to download under
-        if dandiset:
-            identifier = Dandiset._get_identifier(dandiset)
-            if not identifier:
-                raise ValueError(f"Cannot deduce dandiset identifier from {dandiset}")
-            if isinstance(parsed_url, DandisetURL):
-                output_path = op.join(output_dir, identifier)
-                if get_metadata:
-                    for resp in _populate_dandiset_yaml(
-                        output_path, dandiset, existing
-                    ):
-                        yield dict(path=dandiset_metadata_file, **resp)
-            else:
-                output_path = output_dir
-        else:
-            output_path = output_dir
+        if isinstance(parsed_url, DandisetURL) and get_metadata:
+            for resp in _populate_dandiset_yaml(output_path, dandiset, existing):
+                yield dict(path=dandiset_metadata_file, **resp)
 
         # TODO: do analysis of assets for early detection of needed renames etc
         # to avoid any need for late treatment of existing and also for
diff --git a/dandi/tests/test_download.py b/dandi/tests/test_download.py
index a31d8ca29..ff3ab558d 100644
--- a/dandi/tests/test_download.py
+++ b/dandi/tests/test_download.py
@@ -180,3 +180,43 @@ def test_download_asset_id(local_dandi_api, text_dandiset, tmp_path):
         tmp_path / "coconut.txt"
     ]
     assert (tmp_path / "coconut.txt").read_text() == "Coconut\n"
+
+
+@pytest.mark.parametrize("confirm", [True, False])
+def test_download_sync(confirm, local_dandi_api, mocker, text_dandiset, tmp_path):
+    text_dandiset["client"].delete_asset_bypath(
+        text_dandiset["dandiset_id"], "draft", "file.txt"
+    )
+    dspath = tmp_path / text_dandiset["dandiset_id"]
+    os.rename(text_dandiset["dspath"], dspath)
+    confirm_mock = mocker.patch("click.confirm", return_value=confirm)
+    download(
+        f"dandi://{local_dandi_api['instance_id']}/{text_dandiset['dandiset_id']}",
+        tmp_path,
+        existing="overwrite",
+        sync=True,
+    )
+    confirm_mock.assert_called_with("Delete 1 local assets?")
+    if confirm:
+        assert not (dspath / "file.txt").exists()
+    else:
+        assert (dspath / "file.txt").exists()
+
+
+def test_download_sync_folder(local_dandi_api, mocker, text_dandiset):
+    text_dandiset["client"].delete_asset_bypath(
+        text_dandiset["dandiset_id"], "draft", "file.txt"
+    )
+    text_dandiset["client"].delete_asset_bypath(
+        text_dandiset["dandiset_id"], "draft", "subdir2/banana.txt"
+    )
+    confirm_mock = mocker.patch("click.confirm", return_value=True)
+    download(
+        f"dandi://{local_dandi_api['instance_id']}/{text_dandiset['dandiset_id']}/subdir2/",
+        text_dandiset["dspath"],
+        existing="overwrite",
+        sync=True,
+    )
+    confirm_mock.assert_called_with("Delete 1 local assets?")
+    assert (text_dandiset["dspath"] / "file.txt").exists()
+    assert not (text_dandiset["dspath"] / "subdir2" / "banana.txt").exists()

From b86d5f8bec4964da3da0017edbfbe4962508a3a6 Mon Sep 17 00:00:00 2001
From: "John T. Wodder II" <git@varonathe.org>
Date: Fri, 7 May 2021 16:08:45 -0400
Subject: [PATCH 3/4] Proper pluralization

---
 dandi/download.py            | 13 +++++++++++--
 dandi/tests/test_download.py |  4 ++--
 dandi/tests/test_upload.py   |  4 ++--
 dandi/upload.py              |  6 ++++--
 dandi/utils.py               |  9 +++++++++
 5 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/dandi/download.py b/dandi/download.py
index 16d612953..bcc680f68 100644
--- a/dandi/download.py
+++ b/dandi/download.py
@@ -17,7 +17,14 @@
 from .dandiset import Dandiset
 from . import get_logger
 from .support.pyout import naturalsize
-from .utils import ensure_datetime, find_files, flattened, is_same_time, on_windows
+from .utils import (
+    ensure_datetime,
+    find_files,
+    flattened,
+    is_same_time,
+    on_windows,
+    pluralize,
+)
 
 lgr = get_logger()
 
@@ -125,7 +132,9 @@ def download(
                 a_path = a_path.replace("\\", "/")
             if a_path not in asset_paths:
                 to_delete.append(p)
-        if to_delete and click.confirm(f"Delete {len(to_delete)} local assets?"):
+        if to_delete and click.confirm(
+            f"Delete {pluralize(len(to_delete), 'local asset')}?"
+        ):
             for p in to_delete:
                 os.unlink(p)
 
diff --git a/dandi/tests/test_download.py b/dandi/tests/test_download.py
index ff3ab558d..fda8cb95c 100644
--- a/dandi/tests/test_download.py
+++ b/dandi/tests/test_download.py
@@ -196,7 +196,7 @@ def test_download_sync(confirm, local_dandi_api, mocker, text_dandiset, tmp_path
         existing="overwrite",
         sync=True,
     )
-    confirm_mock.assert_called_with("Delete 1 local assets?")
+    confirm_mock.assert_called_with("Delete 1 local asset?")
     if confirm:
         assert not (dspath / "file.txt").exists()
     else:
@@ -217,6 +217,6 @@ def test_download_sync_folder(local_dandi_api, mocker, text_dandiset):
         existing="overwrite",
         sync=True,
     )
-    confirm_mock.assert_called_with("Delete 1 local assets?")
+    confirm_mock.assert_called_with("Delete 1 local asset?")
     assert (text_dandiset["dspath"] / "file.txt").exists()
     assert not (text_dandiset["dspath"] / "subdir2" / "banana.txt").exists()
diff --git a/dandi/tests/test_upload.py b/dandi/tests/test_upload.py
index d53d9ab84..47a55469e 100644
--- a/dandi/tests/test_upload.py
+++ b/dandi/tests/test_upload.py
@@ -158,7 +158,7 @@ def test_upload_sync(confirm, mocker, text_dandiset):
     (text_dandiset["dspath"] / "file.txt").unlink()
     confirm_mock = mocker.patch("click.confirm", return_value=confirm)
     text_dandiset["reupload"](sync=True)
-    confirm_mock.assert_called_with("Delete 1 assets on server?")
+    confirm_mock.assert_called_with("Delete 1 asset on server?")
     asset = text_dandiset["client"].get_asset_bypath(
         text_dandiset["dandiset_id"], "draft", "file.txt"
     )
@@ -173,7 +173,7 @@ def test_upload_sync_folder(mocker, text_dandiset):
     (text_dandiset["dspath"] / "subdir2" / "banana.txt").unlink()
     confirm_mock = mocker.patch("click.confirm", return_value=True)
     text_dandiset["reupload"](paths=[text_dandiset["dspath"] / "subdir2"], sync=True)
-    confirm_mock.assert_called_with("Delete 1 assets on server?")
+    confirm_mock.assert_called_with("Delete 1 asset on server?")
     assert (
         text_dandiset["client"].get_asset_bypath(
             text_dandiset["dandiset_id"], "draft", "file.txt"
diff --git a/dandi/upload.py b/dandi/upload.py
index 8695f5a46..7ace87bf1 100644
--- a/dandi/upload.py
+++ b/dandi/upload.py
@@ -8,7 +8,7 @@
 
 from .consts import dandiset_identifier_regex, dandiset_metadata_file
 from . import lgr
-from .utils import ensure_datetime, get_instance
+from .utils import ensure_datetime, get_instance, pluralize
 
 
 def upload(
@@ -357,6 +357,8 @@ def upload_agg(*ignored):
                 and not Path(dandiset.path, asset["path"]).exists()
             ):
                 to_delete.append(asset["asset_id"])
-        if to_delete and click.confirm(f"Delete {len(to_delete)} assets on server?"):
+        if to_delete and click.confirm(
+            f"Delete {pluralize(len(to_delete), 'asset')} on server?"
+        ):
             for asset_id in to_delete:
                 client.delete_asset(ds_identifier, "draft", asset_id)
diff --git a/dandi/utils.py b/dandi/utils.py
index c457b32c9..31d74f6e2 100644
--- a/dandi/utils.py
+++ b/dandi/utils.py
@@ -708,3 +708,12 @@ def get_module_version(module: Union[str, types.ModuleType]) -> Optional[str]:
         except Exception as exc:
             lgr.debug("Failed to determine version of the %s: %s", mod_name, exc)
     return version
+
+
+def pluralize(n: int, word: str, plural: Optional[str] = None) -> str:
+    if n == 1:
+        return f"{n} {word}"
+    else:
+        if plural is None:
+            plural = word + "s"
+        return f"{n} {plural}"

From f698a67f8014cb2aa90ebbe9afa5f6e6f8174ea2 Mon Sep 17 00:00:00 2001
From: "John T. Wodder II" <git@varonathe.org>
Date: Mon, 10 May 2021 09:53:31 -0400
Subject: [PATCH 4/4] Add option for user to list to-be-deleted assets when
 doing a sync download

---
 dandi/download.py            | 24 ++++++++++++++++++------
 dandi/tests/test_download.py | 31 +++++++++++++++++++++++++++----
 dandi/utils.py               | 29 +++++++++++++++++++++++++++++
 setup.cfg                    |  2 ++
 4 files changed, 76 insertions(+), 10 deletions(-)

diff --git a/dandi/download.py b/dandi/download.py
index bcc680f68..d0f8abf32 100644
--- a/dandi/download.py
+++ b/dandi/download.py
@@ -8,7 +8,6 @@
 import sys
 import time
 
-import click
 import humanize
 import requests
 
@@ -18,6 +17,7 @@
 from . import get_logger
 from .support.pyout import naturalsize
 from .utils import (
+    abbrev_prompt,
     ensure_datetime,
     find_files,
     flattened,
@@ -132,11 +132,23 @@ def download(
                 a_path = a_path.replace("\\", "/")
             if a_path not in asset_paths:
                 to_delete.append(p)
-        if to_delete and click.confirm(
-            f"Delete {pluralize(len(to_delete), 'local asset')}?"
-        ):
-            for p in to_delete:
-                os.unlink(p)
+        if to_delete:
+            while True:
+                opt = abbrev_prompt(
+                    f"Delete {pluralize(len(to_delete), 'local asset')}?",
+                    "yes",
+                    "no",
+                    "list",
+                )
+                if opt == "list":
+                    for p in to_delete:
+                        print(p)
+                elif opt == "yes":
+                    for p in to_delete:
+                        os.unlink(p)
+                    break
+                else:
+                    break
 
 
 def download_generator(
diff --git a/dandi/tests/test_download.py b/dandi/tests/test_download.py
index fda8cb95c..787dbef3f 100644
--- a/dandi/tests/test_download.py
+++ b/dandi/tests/test_download.py
@@ -189,14 +189,16 @@ def test_download_sync(confirm, local_dandi_api, mocker, text_dandiset, tmp_path
     )
     dspath = tmp_path / text_dandiset["dandiset_id"]
     os.rename(text_dandiset["dspath"], dspath)
-    confirm_mock = mocker.patch("click.confirm", return_value=confirm)
+    confirm_mock = mocker.patch(
+        "dandi.download.abbrev_prompt", return_value="yes" if confirm else "no"
+    )
     download(
         f"dandi://{local_dandi_api['instance_id']}/{text_dandiset['dandiset_id']}",
         tmp_path,
         existing="overwrite",
         sync=True,
     )
-    confirm_mock.assert_called_with("Delete 1 local asset?")
+    confirm_mock.assert_called_with("Delete 1 local asset?", "yes", "no", "list")
     if confirm:
         assert not (dspath / "file.txt").exists()
     else:
@@ -210,13 +212,34 @@ def test_download_sync_folder(local_dandi_api, mocker, text_dandiset):
     text_dandiset["client"].delete_asset_bypath(
         text_dandiset["dandiset_id"], "draft", "subdir2/banana.txt"
     )
-    confirm_mock = mocker.patch("click.confirm", return_value=True)
+    confirm_mock = mocker.patch("dandi.download.abbrev_prompt", return_value="yes")
     download(
         f"dandi://{local_dandi_api['instance_id']}/{text_dandiset['dandiset_id']}/subdir2/",
         text_dandiset["dspath"],
         existing="overwrite",
         sync=True,
     )
-    confirm_mock.assert_called_with("Delete 1 local asset?")
+    confirm_mock.assert_called_with("Delete 1 local asset?", "yes", "no", "list")
     assert (text_dandiset["dspath"] / "file.txt").exists()
     assert not (text_dandiset["dspath"] / "subdir2" / "banana.txt").exists()
+
+
+def test_download_sync_list(capsys, local_dandi_api, mocker, text_dandiset, tmp_path):
+    text_dandiset["client"].delete_asset_bypath(
+        text_dandiset["dandiset_id"], "draft", "file.txt"
+    )
+    dspath = tmp_path / text_dandiset["dandiset_id"]
+    os.rename(text_dandiset["dspath"], dspath)
+    input_mock = mocker.patch("dandi.utils.input", side_effect=["list", "yes"])
+    download(
+        f"dandi://{local_dandi_api['instance_id']}/{text_dandiset['dandiset_id']}",
+        tmp_path,
+        existing="overwrite",
+        sync=True,
+    )
+    assert not (dspath / "file.txt").exists()
+    assert input_mock.call_args_list == [
+        mocker.call("Delete 1 local asset? ([y]es/[n]o/[l]ist): "),
+        mocker.call("Delete 1 local asset? ([y]es/[n]o/[l]ist): "),
+    ]
+    assert capsys.readouterr().out.splitlines()[-1] == str(dspath / "file.txt")
diff --git a/dandi/utils.py b/dandi/utils.py
index 31d74f6e2..aa20c4a17 100644
--- a/dandi/utils.py
+++ b/dandi/utils.py
@@ -717,3 +717,32 @@ def pluralize(n: int, word: str, plural: Optional[str] = None) -> str:
         if plural is None:
             plural = word + "s"
         return f"{n} {plural}"
+
+
+def abbrev_prompt(msg: str, *options: str) -> str:
+    """
+    Prompt the user to input one of several options, which can be entered as
+    either a whole word or the first letter of a word.  All input is handled
+    case-insensitively.  Returns the complete word corresponding to the input,
+    lowercased.
+
+    For example, ``abbrev_prompt("Delete assets?", "yes", "no", "list")``
+    prompts the user with the message ``Delete assets? ([y]es/[n]o/[l]ist): ``
+    and accepts as input ``y`, ``yes``, ``n``, ``no``, ``l``, and ``list``.
+    """
+    options_map = {}
+    optstrs = []
+    for opt in options:
+        opt = opt.lower()
+        if opt in options_map:
+            raise ValueError(f"Repeated option: {opt}")
+        elif opt[0] in options_map:
+            raise ValueError(f"Repeated abbreviated option: {opt[0]}")
+        options_map[opt] = opt
+        options_map[opt[0]] = opt
+        optstrs.append(f"[{opt[0]}]{opt[1:]}")
+    msg += " (" + "/".join(optstrs) + "): "
+    while True:
+        answer = input(msg).lower()
+        if answer in options_map:
+            return options_map[answer]
diff --git a/setup.cfg b/setup.cfg
index 6239822ee..22b10b6eb 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -117,3 +117,5 @@ parentdir_prefix =
 
 [codespell]
 skip = dandi/_version.py,dandi/due.py,versioneer.py
+# Don't warn about "[l]ist" in the abbrev_prompt() docstring:
+ignore-regex = \[\w\]\w+