Add snapshot remote repo to build resolution and build.properties.default

Patch by Josh McKenzie; reviewed by Mick Semb Wever and Brandon Williams for CASSANDRA-19810

Author: jmckenzie-dev

.build/build-resolver.xml

@@ -56,8 +56,19 @@
         <resolver:remoterepos id="all">
             <remoterepo id="resolver-central" url="${artifact.remoteRepository.central}"/>
             <remoterepo id="resolver-apache" url="${artifact.remoteRepository.apache}"/>
-            <!-- Snapshots are not allowed, but for feature branches they may be needed, so uncomment the below to allow snapshots to work -->
-            <!-- <remoterepo id="resolver-apache-snapshot" url="https://repository.apache.org/content/repositories/snapshots" releases="false" snapshots="true" updates="always" checksums="fail" /> -->
+            <!-- Snapshot artifacts must not exist in nor be downloaded by any Cassandra release artifact.
+                 Please validate that all artifacts included in parent-pom-template.xml are release
+                 artifacts before committing.
+
+                 To build with a snapshot dependency, ensure build.properties or build.properties.default
+                 contain the correct resolution for "artifact.remoteRepository.apacheSnapshot" and uncomment
+                 the following line.
+
+                 You may also need to add an exclusion for "resolver-apache-snapshot" to your mirrors in ~/.m2/settings.xml
+                 or ~/.ant/settings.xml (maven ant resolver supersedes) as mirrors will, by default, catch and override
+                 all dependency resolution regardless of it being a -SNAPSHOT lib or not.
+             -->
+            <!-- <remoterepo id="resolver-apache-snapshot" url="${artifact.remoteRepository.apacheSnapshot}" releases="false" snapshots="true" updates="always" checksums="fail" /> -->
         </resolver:remoterepos>
 
         <macrodef name="resolve">

build.properties.default

@@ -20,4 +20,4 @@
 #
 artifact.remoteRepository.central:     https://repo1.maven.org/maven2
 artifact.remoteRepository.apache:      https://repo.maven.apache.org/maven2
-
+artifact.remoteRepository.apacheSnapshot: https://repository.apache.org/content/repositories/snapshots