Explicitly forbid the EXECUTOR_NUMBER field

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>

Author: oleg-nenashev

src/main/java/hudson/plugins/perforce/PerforceSCM.java

@@ -2013,6 +2013,11 @@ public FormValidation doValidatePerforceLogin(StaplerRequest req) {
 
         /**
          * Checks to see if the specified workspace is valid.
+         * The method also checks forbidden variables in the client name.
+         * (see <a href="https://wiki.jenkins-ci.org/display/JENKINS/Perforce+Plugin">
+         * Perforce Plugin Wiki page</a>) 
+         * to get the clarification of forbidden variables.
+         * An improper usage of the variable may corrupt Perforce workspaces in project builds. 
          */
         public FormValidation doValidateP4Client(StaplerRequest req) {
             String workspace = Util.fixEmptyAndTrim(req.getParameter("client"));          
@@ -2025,6 +2030,14 @@ public FormValidation doValidateP4Client(StaplerRequest req) {
                     return FormValidation.error("Client name doesn't meet global pattern: "+getP4ClientPattern());
                 }
 
+                // Check forbidden variables
+                for (String variableName : P4CLIENT_FORBIDDEN_VARIABLES) {
+                    if (MacroStringHelper.containsVariable(workspace, variableName)) {
+                        return FormValidation.error(hudson.plugins.perforce.Messages.
+                                PerforceSCM_doValidateP4Client_forbiddenVariableError(variableName));
+                    }
+                }
+                
                 // Then, check depot 
                 Depot depot = getDepotFromRequest(req);
                 if (depot == null) {
@@ -2364,7 +2377,10 @@ public void onRenamed(Item item, String oldName, String newName) {
             Pattern.compile("^\\s*([+-]?//\\S+?/\\S+)\\s+\"//\\S+?(/[^\"]+)\"\\s*$");
     private static final Pattern QUOTED_DEPOT_AND_WORKSPACE =
             Pattern.compile("^\\s*\"([+-]?//\\S+?/[^\"]+)\"\\s+//\\S+?(/\\S+)$\\s*");
-
+    private static final String[] P4CLIENT_FORBIDDEN_VARIABLES= 
+            {"EXECUTOR_NUMBER"};
+    
+    
     /**
      * Parses the projectPath into a list of pairs of strings representing the depot and client
      * paths. Even items are depot and odd items are client.

src/main/java/hudson/plugins/perforce/utils/MacroStringHelper.java

@@ -192,6 +192,16 @@ public static boolean containsMacro(@CheckForNull String str) {
         return str != null && str.matches(".*\\$\\{.*\\}.*");
     }
 
+    /**
+     * Check if the input string contains the specified variable reference.
+     * @param str String to be checked
+     * @param variableName Variable name
+     * @return true if the string contains the specified variable
+     */
+    public static boolean containsVariable(@CheckForNull String str, @Nonnull String variableName) {
+        return str != null && str.matches(".*\\$\\{" + variableName + "\\}.*");
+    }
+    
      /**
      * Substitute parameters and validate contents of the resulting string.
      * This is a keystone method of {@link MacroStringHelper}. 

src/main/resources/hudson/plugins/perforce/Messages.properties

@@ -1 +1,6 @@
-PerforceToolInstallation.onLoaded=Checking p4 executable migration
+PerforceToolInstallation.onLoaded=Checking p4 executable migration
+
+PerforceSCM.doValidateP4Client.forbiddenVariableError= \
+    The {0} variable is forbidden for the client (see the plugin's Wiki page). \
+    An improper usage of the variable may corrupt Perforce workspaces in your build. \
+    Use the variable on your own risk.