RFC: Enable Eclipse warning about fall-through cases in switch statements

Enable the "'switch' case fall-through" warning in Eclipse to catch
unintentional fall-through to the following 'case' block when a 'break'
statement is omitted.

All warnings raised in the current codebase are caused by intentional
fall-throughs, so add "//$FALL-THROUGH$" comments to suppress those
warnings.

This change was inspired by the coverity report [1] which found the
problem in PutConfig (see CID 19880) but interestingly did not report
anything for the other ones.

RFC because I'm not sure if the "//$FALL-THROUGH$" comments will cause
the warnings to be suppressed on subsequent coverity scans.

[1] https://scan.coverity.com/projects/4032

Change-Id: Iad003bd7d086c67cccdbfb1312c8bd82d17fcc57

.settings/org.eclipse.jdt.core.prefs

@@ -17,7 +17,7 @@ org.eclipse.jdt.core.compiler.problem.deprecationWhenOverridingDeprecatedMethod=
 org.eclipse.jdt.core.compiler.problem.discouragedReference=warning
 org.eclipse.jdt.core.compiler.problem.emptyStatement=warning
 org.eclipse.jdt.core.compiler.problem.explicitlyClosedAutoCloseable=ignore
-org.eclipse.jdt.core.compiler.problem.fallthroughCase=ignore
+org.eclipse.jdt.core.compiler.problem.fallthroughCase=warning
 org.eclipse.jdt.core.compiler.problem.fatalOptionalError=disabled
 org.eclipse.jdt.core.compiler.problem.fieldHiding=warning
 org.eclipse.jdt.core.compiler.problem.finalParameterBound=warning

gerrit-server/src/main/java/com/google/gerrit/server/change/Submit.java

@@ -227,6 +227,7 @@ public class Submit implements RestModifyView<RevisionResource, SubmitInput>,
         if (msg != null) {
           throw new ResourceConflictException(msg.getMessage());
         }
+        //$FALL-THROUGH$
       default:
         throw new ResourceConflictException("change is " + status(change));
     }

gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java

@@ -1733,6 +1733,7 @@ public class ReceiveCommits {
             addMessage("Change " + c.getChangeId() + ": " + msg.getMessage());
             break;
           }
+          //$FALL-THROUGH$
         default:
           addMessage("change " + c.getChangeId() + " is "
               + c.getStatus().name().toLowerCase());

gerrit-server/src/main/java/com/google/gerrit/server/project/CreateBranch.java

@@ -166,6 +166,7 @@ public class CreateBranch implements RestModifyView<ProjectResource, Input> {
               }
               refPrefix = getRefPrefix(refPrefix);
             }
+            //$FALL-THROUGH$
           default: {
             throw new IOException(result.name());
           }

gerrit-server/src/main/java/com/google/gerrit/server/project/PutConfig.java

@@ -253,6 +253,7 @@ public class PutConfig implements RestModifyView<ProjectResource, Input> {
                           "The value '%s' is not permitted for parameter '%s' of plugin '"
                               + pluginName + "'", value, v.getKey()));
                     }
+                    //$FALL-THROUGH$
                   case STRING:
                     cfg.setString(v.getKey(), value);
                     break;