Reduce repetition

.gitlab-ci.yml

-build-deb:jessie:
-  stage: build
-  image: containers.ethitter.com:443/docker/images/debian:jessie
 before_script:
-    - echo $NGINX_VERSION_JESSIE
-    - echo $NGINX_BINARY_JESSIE
+  - echo $NGINX_VERSION
+  - echo $NGINX_BINARY
 
   # Relies on latest binary build artifact from https://git.ethitter.com/debian/nginx-build.
-    - curl -o nginx-build "${NGINX_BINARY_JESSIE}"
+  - curl -o nginx-build "${NGINX_BINARY}"
   - chmod +x nginx-build
   - ./nginx-build -V
+
+build-deb:jessie:
+  stage: build
+  image: containers.ethitter.com:443/docker/images/debian:jessie
+  variables:
+    NGINX_BINARY: $NGINX_BINARY_JESSIE
+    NGINX_VERSION: $NGINX_VERSION_JESSIE
   script:
     - cd source
     - debuild -us -uc
   artifacts:
     paths:
-      - nginx_${NGINX_VERSION_JESSIE}*
+      - nginx_${NGINX_VERSION}*
       - nginx-dbgsym_*
 
 test-deb:jessie:
   stage: test
   image: containers.ethitter.com:443/docker/images/debian:jessie
+  before_script:
+    - date
   script:
     - dpkg -i nginx_${NGINX_VERSION_JESSIE}*.deb
     - nginx -V
@@ -29,25 +35,22 @@ test-deb:jessie:
 build-deb:stretch:
   stage: build
   image: containers.ethitter.com:443/docker/images/debian:stretch
-  before_script:
-    - echo $NGINX_VERSION_STRETCH
-    - echo $NGINX_BINARY_STRETCH
-
-    # Relies on latest binary build artifact from https://git.ethitter.com/debian/nginx-build.
-    - curl -o nginx-build "${NGINX_BINARY_STRETCH}"
-    - chmod +x nginx-build
-    - ./nginx-build -V
+  variables:
+    NGINX_BINARY: $NGINX_BINARY_STRETCH
+    NGINX_VERSION: $NGINX_VERSION_STRETCH
   script:
     - cd source
     - debuild -us -uc
   artifacts:
     paths:
-      - nginx_${NGINX_VERSION_STRETCH}*
+      - nginx_${NGINX_VERSION}*
       - nginx-dbgsym_*
 
 test-deb:stretch:
   stage: test
   image: containers.ethitter.com:443/docker/images/debian:stretch
+  before_script:
+    - date
   script:
     - dpkg -i nginx_${NGINX_VERSION_STRECTH}*.deb
     - nginx -V
@@ -57,25 +60,22 @@ test-deb:stretch:
 build-deb:buster:
   stage: build
   image: containers.ethitter.com:443/docker/images/debian:buster
-  before_script:
-    - echo $NGINX_VERSION_BUSTER
-    - echo $NGINX_BINARY_BUSTER
-
-    # Relies on latest binary build artifact from https://git.ethitter.com/debian/nginx-build.
-    - curl -o nginx-build "${NGINX_BINARY_BUSTER}"
-    - chmod +x nginx-build
-    - ./nginx-build -V
+  variables:
+    NGINX_BINARY: $NGINX_BINARY_BUSTER
+    NGINX_VERSION: $NGINX_VERSION_BUSTER
   script:
     - cd source
     - debuild -us -uc
   artifacts:
     paths:
-      - nginx_${NGINX_VERSION_BUSTER}*
+      - nginx_${NGINX_VERSION}*
       - nginx-dbgsym_*
 
 test-deb:buster:
   stage: test
   image: containers.ethitter.com:443/docker/images/debian:buster
+  before_script:
+    - date
   script:
     - dpkg -i nginx_${NGINX_VERSION_BUSTER}*.deb
     - nginx -V