Merge #20680: ci: Only use credits for pull requests to the main repo

facf5e37f619be6bd7f8768058842679cd9ad933 ci: Only use credits for pull requests to the main repo (MarcoFalke)

Pull request description:

  No need to spend credits for the `master` branch, because the build shouldn't fail there anyway and it is not time-critical to get a fast feedback.

  Some other changes:

  * Disable `stateful` for faster scheduling
  * Reduce lint memory from 8G to 1G for faster scheduling

ACKs for top commit:
  hebasto:
    ACK facf5e37f619be6bd7f8768058842679cd9ad933, I have reviewed the code and it looks OK, I agree it can be merged.

Tree-SHA512: 4d052e68217086574b9ea3d603cde1b585833c289d47dfed5308ff001d02964dc75ec3b3ebf5b233ccd09c47ad4ff5ba0bef639bf6362d984e7c49fca8fec24b

.cirrus.yml

@@ -9,10 +9,9 @@ env:
   CCACHE_SIZE: "200M"
   CCACHE_DIR: "/tmp/ccache_dir"
 
-### Base template
 # https://cirrus-ci.org/guide/tips-and-tricks/#sharing-configuration-between-tasks
 base_template: &BASE_TEMPLATE
-  skip: $CIRRUS_REPO_FULL_NAME == "bitcoin-core/gui" && $CIRRUS_PR == "" # No need to run on the read-only mirror, unless it is a PR. https://cirrus-ci.org/guide/writing-tasks/#conditional-task-execution
+  skip: $CIRRUS_REPO_FULL_NAME == "bitcoin-core/gui" && $CIRRUS_PR == ""  # No need to run on the read-only mirror, unless it is a PR. https://cirrus-ci.org/guide/writing-tasks/#conditional-task-execution
   merge_base_script:
     - if [ "$CIRRUS_PR" = "" ]; then exit 0; fi
     - bash -c "$PACKAGE_MANAGER_INSTALL git"
@@ -20,8 +19,8 @@ base_template: &BASE_TEMPLATE
     - git config --global user.email "ci@ci.ci"
     - git config --global user.name "ci"
     - git merge FETCH_HEAD  # Merge base to detect silent merge conflicts
+  stateful: false  # https://cirrus-ci.org/guide/writing-tasks/#stateful-tasks
 
-### Global task template
 global_task_template: &GLOBAL_TASK_TEMPLATE
   << : *BASE_TEMPLATE
   timeout_in: 120m  # https://cirrus-ci.org/faq/#instance-timed-out
@@ -42,15 +41,21 @@ global_task_template: &GLOBAL_TASK_TEMPLATE
   ci_script:
     - ./ci/test_run_all.sh
 
+compute_credits_template: &CREDITS_TEMPLATE
+  # https://cirrus-ci.org/pricing/#compute-credits
+  # Only use credits for pull requests to the main repo
+  use_compute_credits: $CIRRUS_REPO_FULL_NAME == 'dashpay/dash' && $CIRRUS_PR != ""
+
 
 task:
-  name: 'lint'
+  name: 'lint [bionic]'
   << : *BASE_TEMPLATE
   container:
-    image: ubuntu:bionic # For python 3.6, oldest supported version according to doc/dependencies.md
-    cpu: 1 # Cut bill in half for linting
-  # For faster CI feedback, immediately schedule the linters. https://cirrus-ci.org/pricing/#compute-credits
-  use_compute_credits: $CIRRUS_REPO_FULL_NAME == 'dashpay/dash'
+    image: ubuntu:bionic  # For python 3.6, oldest supported version according to doc/dependencies.md
+    cpu: 1
+    memory: 1G
+  # For faster CI feedback, immediately schedule the linters
+  << : *CREDITS_TEMPLATE
   setup_script:
     - set -o errexit; source ./ci/test/00_setup_env.sh
   before_install_script:
@@ -92,8 +97,8 @@ task:
 
 task:
   name: '[previous releases, uses qt5 dev package and some depends packages] [unsigned char] [focal]'
-  # For faster CI feedback, immediately schedule a task that compiles most modules. https://cirrus-ci.org/pricing/#compute-credits
-  use_compute_credits: $CIRRUS_REPO_FULL_NAME == 'dashpay/dash'
+  # For faster CI feedback, immediately schedule a task that compiles most modules
+  << : *CREDITS_TEMPLATE
   << : *GLOBAL_TASK_TEMPLATE
   container:
     image: ubuntu:focal