gitlab-ci: rename the CI jobs.

The Linux CI job names are too long and are not recognizable on the web
GUI unless you hover the widgets with the mouse to read tooltips. Remove
the "/testing" part (if people want to know exactly which Debian we use
for our builds, they can always look at the script) and move left the
differenciating parts (i.e. autotools/meson/clang/distcheck) so that
these are visible in a glance, even when ellipsing long job names.

.gitlab-ci.yml

@@ -71,9 +71,9 @@ build-image-win32:
     - /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile --destination $CI_REGISTRY_IMAGE:build-win32-latest --cache=true --cache-ttl=120h
 
 
-## GNU/Linux 64-bit CIs ##
+## GNU/Linux 64-bit CIs (Debian testing) ##
 
-deps-debian/testing:
+deps-debian:
   stage: dependencies
   image: $CI_REGISTRY_IMAGE:build-debian-latest
   cache:
@@ -105,11 +105,11 @@ deps-debian/testing:
     - ninja -C _build install
   needs: ["build-image"]
 
-.gimp-debian/testing-base:
+.gimp-debian-base:
   stage: gimp
   image: $CI_REGISTRY_IMAGE:build-debian-latest
   dependencies:
-    - deps-debian/testing
+    - deps-debian
   cache:
     paths:
     - apt-cache
@@ -128,10 +128,10 @@ deps-debian/testing:
     - export LD_LIBRARY_PATH="${INSTALL_PREFIX}/lib/`gcc -print-multiarch`:$LD_LIBRARY_PATH"
     - export XDG_DATA_DIRS="${INSTALL_PREFIX}/share:/usr/local/share:/usr/share"
     - export PATH="${INSTALL_PREFIX}/bin:$PATH"
-  needs: ["deps-debian/testing"]
+  needs: ["deps-debian"]
 
-gimp-debian/testing-autotools:
-  extends: .gimp-debian/testing-base
+gimp-autotools-debian:
+  extends: .gimp-debian-base
   script:
     - mkdir _build
     - cd _build
@@ -144,8 +144,8 @@ gimp-debian/testing-autotools:
     - make -j "$(nproc)"
     - make check
 
-gimp-debian/testing-autotools-distcheck:
-  extends: .gimp-debian/testing-base
+gimp-distcheck-debian:
+  extends: .gimp-debian-base
   script:
     - mkdir _build
     - cd _build
@@ -160,8 +160,8 @@ gimp-debian/testing-autotools-distcheck:
     - make distcheck
   allow_failure: true
 
-gimp-debian/testing-meson:
-  extends: .gimp-debian/testing-base
+gimp-meson-debian:
+  extends: .gimp-debian-base
   script:
     - meson _build
       --prefix="${INSTALL_PREFIX}"
@@ -171,8 +171,8 @@ gimp-debian/testing-meson:
     - ninja -C _build
     - ninja -C _build test
 
-gimp-debian/testing-clang:
-  extends: .gimp-debian/testing-base
+gimp-clang-debian:
+  extends: .gimp-debian-base
   variables:
     CC: "clang"
     CXX: "clang++"