Try slurp

ansible/pre-deploy.yml

@@ -8,17 +8,23 @@
         extensions:
           - yml
 
-    - name: Retrieve git user ssh public key
-      set_fact:
-        git_ssh_pub_key: "{{ lookup('file', '/home/git/.ssh/id_rsa.pub') }}"
-        git_auth_keys: "{{ lookup('file', '/var/lib/gitea/git/.ssh/authorized_keys') }}"
+    - name: Slurp the git user ssh public key
+      slurp:
+        src: /home/git/.ssh/id_rsa.pub
+      register: git_id_rsa
+      become: true
+
+    - name: Slurp the git user ssh authorized_keys
+      slurp:
+        src: /var/lib/gitea/git/.ssh/authorized_keys
+      register: git_auth_keys
       become: true
 
     - name: TEST TEST TEST
       lineinfile:
         path: /var/lib/gitea/git/.ssh/authorized_keys
-        regexp: "^{{ git_ssh_pub_key }}"
-        line: "{{ git_ssh_pub_key }}{{ git_auth_keys }}"
+        regexp: "^{{ git_id_rsa['content'] }}"
+        line: "{{ git_id_rsa['content'] }}{{ git_auth_keys['content'] }}"
         state: present
         create: true
       become: true