Make the ability to remove reviewers a grantable permission

Change-Id: I4ee3c3b6a42916bc3bb6d4283c937552033f309c

Documentation/access-control.txt

@@ -728,6 +728,20 @@ Users without this access right who are able to upload new patch sets
 can still do the rebase locally and upload the rebased commit as a new
 patch set.
 
+[[category_remove_reviewer]]
+Remove Reviewer
+~~~~~~~~~~~~~~~
+
+This category permits users to remove other users from the list of
+reviewers on a change.
+
+The change owner, project owner and site administrator can always
+remove reviewers (even without having the `Remove Reviewer` access
+right assigned).
+
+Users without this access right can only remove themselves from the
+reviewer list on a change.
+
 
 [[category_submit]]
 Submit

gerrit-common/src/main/java/com/google/gerrit/common/data/Permission.java

@@ -33,6 +33,7 @@ public class Permission implements Comparable<Permission> {
   public static final String PUSH_TAG = "pushTag";
   public static final String READ = "read";
   public static final String REBASE = "rebase";
+  public static final String REMOVE_REVIEWER = "removeReviewer";
   public static final String SUBMIT = "submit";
 
   private static final List<String> NAMES_LC;
@@ -52,6 +53,7 @@ public class Permission implements Comparable<Permission> {
     NAMES_LC.add(PUSH_TAG.toLowerCase());
     NAMES_LC.add(LABEL.toLowerCase());
     NAMES_LC.add(REBASE.toLowerCase());
+    NAMES_LC.add(REMOVE_REVIEWER.toLowerCase());
     NAMES_LC.add(SUBMIT.toLowerCase());
 
     labelIndex = NAMES_LC.indexOf(Permission.LABEL);

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/AdminConstants.properties

@@ -114,6 +114,7 @@ permissionNames = \
 	pushTag, \
 	read, \
 	rebase, \
+	removeReviewer, \
 	submit
 abandon = Abandon
 create = Create Reference
@@ -126,6 +127,7 @@ pushMerge = Push Merge Commit
 pushTag = Push Annotated Tag
 read = Read
 rebase = Rebase
+removeReviewer = Remove Reviewer
 submit = Submit
 
 refErrorEmpty = Reference must be supplied

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

@@ -282,9 +282,10 @@ public class ChangeControl {
         return true;
       }
 
-      // The branch owner, project owner, site admin can remove anyone.
+      // Users with the remove reviewer permission, the branch owner, project
-      //
+      // owner and site admin can remove anyone
-      if (getRefControl().isOwner() // branch owner
+      if (getRefControl().canRemoveReviewer() // has removal permissions
+          || getRefControl().isOwner() // branch owner
           || getProjectControl().isOwner() // project owner
           || getCurrentUser().getCapabilities().canAdministrateServer()) {
         return true;

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

@@ -322,6 +322,11 @@ public class RefControl {
     return canPerform(Permission.ABANDON);
   }
 
+  /** @return true if this user can remove a reviewer for a change. */
+  public boolean canRemoveReviewer() {
+    return canPerform(Permission.REMOVE_REVIEWER);
+  }
+
   /** All value ranges of any allowed label permission. */
   public List<PermissionRange> getLabelRanges() {
     List<PermissionRange> r = new ArrayList<PermissionRange>();