Fail if merge to enterprise causes compilation issues (#4027)

* check compilation of enterprise job

* test that enterprise merge job fails with compilation error

* Revert "test that enterprise merge job fails with compilation error"

This reverts commit 0eaccd58c207a4c15365186017bf47601cc95552.

* Update readme and use citus extbuilder:13beta3

.circleci/config.yml

@@ -488,7 +488,7 @@ jobs:
 
   check-merge-to-enterprise:
     docker:
-      - image: buildpack-deps:stretch
+      - image: citus/extbuilder:13beta3
     working_directory: /home/circleci/project
     steps:
       - checkout

ci/README.md

@@ -51,11 +51,13 @@ following:
 This check exists to make sure that we can always merge the `master` branch of
 `community` into the `enterprise-master` branch of the `enterprise` repo.
 There are two conditions in which this check passes:
-1. There are no merge conflicts between your PR branch and `enterprise-master`.
+
+1. There are no merge conflicts between your PR branch and `enterprise-master` and after this merge the code compiles.
 2. There are merge conflicts, but there is a branch with the same name in the
    enterprise repo that:
    1. Contains the last commit of the community branch with the same name.
    2. Merges cleanly into `enterprise-master`
+3. After merging, the code can be compiled.
 
 If the job already passes, you are done, nothing further required! Otherwise
 follow the below steps.

ci/check_enterprise_merge.sh

@@ -22,6 +22,12 @@ source ci/ci_helpers.sh
 # are not shown in CI output (even though it's also filtered out by CircleCI)
 set -x
 
+check_compile () {
+    echo "INFO: checking if merged code can be compiled"
+    ./configure --without-libcurl
+    make -j10
+}
+
 # Clone current git repo (which should be community) to a temporary working
 # directory and go there
 GIT_DIR_ROOT="$(git rev-parse --show-toplevel)"
@@ -47,7 +53,9 @@ git fetch enterprise enterprise-master
 git checkout "enterprise/enterprise-master"
 
 if git merge --no-commit "origin/$PR_BRANCH"; then
-    echo "INFO: community PR branch could be merged into enterprise-master, so everything is good"
+    echo "INFO: community PR branch could be merged into enterprise-master"
+    # check that we can compile after the merge
+    check_compile
     exit 0
 fi
 
@@ -73,3 +81,5 @@ fi
 # Now check if we can merge the enterprise PR into enterprise-master without
 # issues.
 git merge --no-commit "enterprise/$PR_BRANCH"
+# check that we can compile after the merge
+check_compile