Newbie tries to add a snippet to an origin

[divoplade <d@divoplade.fr>]

Hello,

I am trying to add a file named ".tarball-version" containing a fixed
string at the root of my source.

I tried several things, the most promising (I think) being this:

(define-public pomdappi-dist
  (dist-package
   pomdappi
   (origin
     (method git-fetch)
     (uri (git-reference
           (url "@REPO@")
           (commit "@COMMIT@")))
     (sha256
      (base32
       "@COMMIT_BASE32@"))
     (snippet
      #~(symlink #$(plain-file ".tarball-version" "@VERSION@")
                 ".tarball-version")))))

However, I get "guix build: error: invalid name: `.tarball-version'"
when running guix build.

My idea was to create a file in the store containing the fixed string
@VERSION@, and then symlink it withing the source as ".tarball-
version".

Could someone help me?

divoplade