ci: checkpatch scans the entire MR

Summary

• ci: checkpatch scans the entire MR

NO_DOC=internal NO_TEST=internal NO_CHANGELOG=internal

Close #28 (closed) Docs follow-up: not necessary / new issue

.gitlab-ci.yml

@@ -50,7 +50,7 @@ variables:
       # implies compare_to HEAD~1
       paths: &build-base-changes-paths
         - docker/**
-#        - .gitlab-ci.yml 
+        - .gitlab-ci.yml
 
   - &if-build-base-changes-on-dev-branch
     if: $CI_COMMIT_BRANCH != $MAIN_BRANCH
@@ -150,9 +150,10 @@ checkpatch:
     tags: [shell_p_t]
     script:
       - git clone --depth 1 git@github.com:tarantool/checkpatch.git
-      - git fetch origin $CI_MERGE_REQUEST_TARGET_BRANCH_SHA
-      - COUNT_COMMIT=$(git log --pretty=oneline HEAD...origin/$CI_MERGE_REQUEST_TARGET_BRANCH_SHA | wc -l)
+      - git fetch origin $CI_DEFAULT_BRANCH
+      - COUNT_COMMIT=$(git log --pretty=oneline HEAD...origin/$CI_DEFAULT_BRANCH | wc -l)
       - checkpatch/checkpatch.pl --color=always --git HEAD~${COUNT_COMMIT}..HEAD
+      
 
 # run long tests and coverage on release build
 coverage: