Drop compatibility with CMake < 2.4

Drop all behavior activated by setting CMAKE_BACKWARDS_COMPATIBILITY to
a value lower than 2.4, and generate an error when projects or the user
attempt to do so.  In the error suggest using a CMake 2.8.x release.

Teach cmake_minimum_required to warn about projects that do not require
at least CMake 2.4.  They are not supported by CMake >= 3.0.

Replace the documentation of CMAKE_BACKWARDS_COMPATIBILITY with a
reference to policy CMP0001.

1 files changed, 4 insertions, 21 deletions

diff --git a/Source/cmConfigureFileCommand.cxx b/Source/cmConfigureFileCommand.cxx
index e52ddef..f8ec642 100644
--- a/Source/cmConfigureFileCommand.cxx
+++ b/Source/cmConfigureFileCommand.cxx
@@ -74,10 +74,6 @@ bool cmConfigureFileCommand
   this->CopyOnly = false;
   this->EscapeQuotes = false;
 
-  // for CMake 2.0 and earlier CONFIGURE_FILE defaults to the FinalPass,
-  // after 2.0 it only does InitialPass
-  this->Immediate = !this->Makefile->NeedBackwardsCompatibility(2,0);
-
   this->AtOnly = false;
   for(unsigned int i=2;i < args.size();++i)
     {
@@ -101,32 +97,19 @@ bool cmConfigureFileCommand
       }
     else if(args[i] == "IMMEDIATE")
       {
-      this->Immediate = true;
+      /* Ignore legacy option.  */
       }
     }
 
-  // If we were told to copy the file immediately, then do it on the
-  // first pass (now).
-  if(this->Immediate)
+  if ( !this->ConfigureFile() )
     {
-    if ( !this->ConfigureFile() )
-      {
-      this->SetError("Problem configuring file");
-      return false;
-      }
+    this->SetError("Problem configuring file");
+    return false;
     }
 
   return true;
 }
 
-void cmConfigureFileCommand::FinalPass()
-{
-  if(!this->Immediate)
-    {
-    this->ConfigureFile();
-    }
-}
-
 int cmConfigureFileCommand::ConfigureFile()
 {
   return this->Makefile->ConfigureFile(