The Debian packaging of git-annex is maintained in git, using the
merging workflow described in dgit-maint-merge(7).  There isn't a
patch queue that can be represented as a quilt series.

A detailed breakdown of the changes is available from their canonical
representation - git commits in the packaging repository.  For
example, to see the changes made by the Debian maintainer in the first
upload of upstream version 1.2.3, you could use:

    % git clone https://git.dgit.debian.org/git-annex
    % cd git-annex
    % git log --oneline 1.2.3..debian/1.2.3-1 -- . ':!debian'

(If you have dgit, use `dgit clone git-annex`, rather than plain `git
clone`.)

A single combined diff, containing all the changes, follows.
--- git-annex-10.20250416.orig/Makefile
+++ git-annex-10.20250416/Makefile
@@ -64,7 +64,7 @@ git-annex: tmp/configure-stamp
 			ln -f $$(cabal list-bin git-annex) git-annex || \
 				ln -f $$(cabal exec -- sh -c 'command -v git-annex') git-annex; \
 		else \
-			ln -f dist/build/git-annex/git-annex git-annex; \
+			rm git-annex; ln -f dist/build/git-annex/git-annex git-annex; \
 		fi; \
 	fi
 
