Upgrade woodpecker config

- Pipeline changed its name to steps.
- Default checkout was target branch, conflicting with our fetch.
- Spliting fetch and actual tests for readability.
- Cannot split apt install as each step runs in a separated
- container (clean way would be to create an image with hunspell in it).

Also I don't remember why there's those git things here, so let's try
without…

.woodpecker.yml

@@ -1,13 +1,37 @@
 ---
 
-pipeline:
+# `make verifs` only checks changed files, so it make sense only on
+# pull requests.
+
+# Also we're using `branch: "$CI_COMMIT_SOURCE_BRANCH"` because the
+# default branch name is the target branch, conflicting with the fact
+# the Makefile tries to compare the current branch to the target
+# branch...
+
+when:
+  event: pull_request
+
+clone:
+  git:
+    image: woodpeckerci/plugin-git
+    pull: true
+    settings:
+      branch: ${CI_COMMIT_SOURCE_BRANCH}
+
+steps:
+  fetch target branch:
+    image: python
+    commands:
+      - BRANCH="$(make print-BRANCH)"
+      - git fetch origin --no-tags +refs/heads/$BRANCH
+      - git branch $BRANCH origin/$BRANCH
+      - git branch -va
+
   test:
     image: python
     commands:
       - apt-get update
       - apt-get install -y hunspell hunspell-fr-comprehensive
       - python3 -m pip install -r requirements.txt
-      - BRANCH="$(grep ^BRANCH Makefile | awk '{print $3}')"
-      - git fetch origin --no-tags +refs/heads/$BRANCH
-      - 'git branch $BRANCH origin/$BRANCH ||:'
+      - make diff
       - make verifs

Makefile

@@ -192,3 +192,11 @@ clean:
 	find -name '*.mo' -delete
 	@echo "Cleaning build directory"
 	$(MAKE) -C venv/cpython/Doc/ clean
+
+.PHONY: diff
+diff:
+	@echo "Files changed between $(BRANCH) and HEAD:"
+	@echo $(shell git diff --name-only --diff-filter=d $(BRANCH))
+
+print-%:
+	@echo $($*)