### Please describe the problem.

Adding a file with a long extension, like Apple Numbers file (for example budget.numbers) results in it being added to the backend without file extension at all.

### What steps will reproduce the problem?
[[!format sh """
$ touch budget.numbers
$ git-annex add budget.numbers
add budget.numbers ok
(recording state in git...)
$ git-annex lookupkey budget.numbers
SKEIN256E-s0--c8877087da56e072870daa843f176e9453115929094c3a40c463a196c29bf7ba
$ touch budget.num
$ git annex add budget.num
add budget.num ok
(recording state in git...)
$ git annex lookupkey budget.num
SKEIN256E-s0--c8877087da56e072870daa843f176e9453115929094c3a40c463a196c29bf7ba.num
"""]]
### What version of git-annex are you using? On what operating system?
[[!format sh """
$ git-annex version
git-annex version: 6.20180807
build flags: Assistant Webapp Pairing S3(multipartupload)(storageclasses) WebDAV FsEvents ConcurrentOutput TorrentParser MagicMime Feeds Testsuite
dependency versions: aws-0.19 bloomfilter-2.0.1.0 cryptonite-0.25 DAV-1.3.2 feed-1.0.0.0 ghc-8.2.2 http-client-0.5.13.1 persistent-sqlite-2.6.4 torrent-10000.1.1 uuid-1.3.13 yesod-1.4.5
key/value backends: SHA256E SHA256 SHA512E SHA512 SHA224E SHA224 SHA384E SHA384 SHA3_256E SHA3_256 SHA3_512E SHA3_512 SHA3_224E SHA3_224 SHA3_384E SHA3_384 SKEIN256E SKEIN256 SKEIN512E SKEIN512 BLAKE2B256E BLAKE2B256 BLAKE2B512E BLAKE2B512 BLAKE2B160E BLAKE2B160 BLAKE2B224E BLAKE2B224 BLAKE2B384E BLAKE2B384 BLAKE2S256E BLAKE2S256 BLAKE2S160E BLAKE2S160 BLAKE2S224E BLAKE2S224 BLAKE2SP256E BLAKE2SP256 BLAKE2SP224E BLAKE2SP224 SHA1E SHA1 MD5E MD5 WORM URL
remote types: git gcrypt p2p S3 bup directory rsync web bittorrent webdav adb tahoe glacier ddar hook external
operating system: darwin x86_64
supported repository versions: 3 5 6
upgrade supported from repository versions: 0 1 2 3 4 5
local repository version: 5
"""]]

macOS 10.13.6

### Please provide any additional information below.

macOS isn't able to open a file without extension. In order to just view it, I have to `git annex unlock` it, so that there's a real file with an extension. Is there a way to tell macOS to use symlink extension instead? Or other workaround?

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)

Yup, I've been using it for 5 years. It's awesome! Thank you.

> [[done]] --[[Joey]]
