Please describe the problem.

Original complaints could be found mentioned in the comments of the importfeed page: when using addurl, and even when the server provides Content-Disposition field with the filename, git-annex seems (BTW -- no Content-Disposition was mentioned in the --debug output) to take that filename value and obfuscates it (replaces '-' with '_' etc) to what supposed to be the original filename.

$> mkdir /tmp/testrepo; cd /tmp/testrepo; git init; git annex init; 
mkdir: cannot create directory ‘/tmp/testrepo’: File exists
E: could not determine git repository root
Initialized empty Git repository in /tmp/testrepo/.git/
init  ok
(recording state in git...)

$> git annex addurl --fast      
addurl (to sub_mouse_AAYYT_ses_20180420_sample_2_slice_20180420_slice_2_cell_20180420_sample_2.nwb) ok
(recording state in git...)

$> ls -l
total 4
lrwxrwxrwx 1 yoh yoh 184 May  7 17:02 sub_mouse_AAYYT_ses_20180420_sample_2_slice_20180420_slice_2_cell_20180420_sample_2.nwb -> .git/annex/objects/Gj/9z/URL-s9335000--https&


whenever original content-disposition was having "-" in the filename, which are perfectly safe the filename AFAIK:

$> wget -S                
... bunch of forwards to the final one with the content disposition field
Resolving (
Connecting to (||:443... connected.
HTTP request sent, awaiting response... 
  HTTP/1.1 200 OK
  x-amz-id-2: VgJE1jV5XUkBQXZDWgR5WEDfmHJp4Fj6fGo6z2tYkLfyTsxDWC+m92B2qOSVppCuiRFu2QpNV5M=
  x-amz-request-id: 1221CAC30E3931CF
  Date: Thu, 07 May 2020 21:02:52 GMT
  Last-Modified: Wed, 22 Apr 2020 00:54:32 GMT
  ETag: "acf3b4f5951435245a0efcd4a518e77d"
  Content-Disposition: attachment; filename="sub-mouse-AAYYT_ses-20180420-sample-2_slice-20180420-slice-2_cell-20180420-sample-2.nwb"

$> git annex version
git-annex version: 7.20190708+git9-gfa3524b95-1~ndall+1

done --Joey