CI: update configuration

* Attempt to use git client provided by CI.
* Set task name to explicitly mark that build is for testing purposes only.

.cirrus.yml

@@ -3,9 +3,14 @@ container:
   cpu: 8
   memory: 16
 
-# Build packages.
-build_task:
-  # 2 hours is a maximal timeout for free use.
+##
+## * Only test build. No uploads here.
+## * Timeout is 120 minutes.
+##
+
+task:
+  name: Test build
+
   timeout_in: 120m
 
   environment:
@@ -15,23 +20,8 @@ build_task:
       TERMUX_ARCH: i686
       TERMUX_ARCH: x86_64
 
-  # Do not use built-in git client provided by Cirrus as may
-  # cause problems when determining changed files.
-  clone_script: |
-    if [[ -z "$CIRRUS_PR" ]]; then
-      git clone --recursive --branch="$CIRRUS_BRANCH" "https://x-access-token:${CIRRUS_REPO_CLONE_TOKEN}@github.com/${CIRRUS_REPO_FULL_NAME}.git" "$CIRRUS_WORKING_DIR"
-      git reset --hard "$CIRRUS_CHANGE_IN_REPO"
-    else
-      git clone --recursive "https://x-access-token:${CIRRUS_REPO_CLONE_TOKEN}@github.com/${CIRRUS_REPO_FULL_NAME}.git" "$CIRRUS_WORKING_DIR"
-      git fetch origin "pull/$CIRRUS_PR/head:pull/$CIRRUS_PR"
-      git reset --hard "$CIRRUS_CHANGE_IN_REPO"
-    fi
-
-  # Following script will determine changes via Git and build
-  # modified packages.
   build_script: |
     bash ./scripts/build/ci/cirrus-ci_dispatcher.sh
 
-  # Make built packages downloadable from web UI.
   output_artifacts:
     path: "./debs/*.deb"