Add addSynchronously flag to ArchiveEntry

plexus-io 2.7 adds support for resource collection that does not allow
concurrent access to it's entries. Add flag to ArchiveEntry so archiver
implementations could know that they should add entries form such
collections synchronously.

Author: Plamen Totev

src/main/java/org/codehaus/plexus/archiver/ArchiveEntry.java

@@ -60,6 +60,8 @@ public class ArchiveEntry
 
     private PlexusIoResourceAttributes attributes;
 
+    private final boolean addSynchronously;
+
     /**
      * @param name     the filename as it will appear in the archive. This is platform-specific
      *                 normalized with File.separatorChar
@@ -92,6 +94,8 @@ private ArchiveEntry( String name, @Nonnull PlexusIoResource resource, int type,
 
         this.mode = permissions == -1 ? permissions : ( permissions & UnixStat.PERM_MASK ) |
             ( type == FILE ? UnixStat.FILE_FLAG : type == SYMLINK ? UnixStat.LINK_FLAG : UnixStat.DIR_FLAG );
+
+        this.addSynchronously = ( collection != null && !collection.isConcurrentAccessSupported() );
     }
 
     /**
@@ -154,6 +158,17 @@ public int getMode()
             ( type == FILE ? UnixStat.FILE_FLAG : type == SYMLINK ? UnixStat.LINK_FLAG : UnixStat.DIR_FLAG );
     }
 
+    /**
+     * Indicates if this entry should be added to the archive synchronously
+     * before adding the next entry and/or accessing the next entry of {@link ResourceIterator}. 
+     * 
+     * @return {@code true} if this entry should be added synchronously
+     */
+    public boolean shouldAddSynchronously()
+    {
+        return addSynchronously;
+    }
+
     public static ArchiveEntry createFileEntry( String target, PlexusIoResource resource, int permissions,
                                                 PlexusIoResourceCollection collection, int defaultDirectoryPermissions )
         throws ArchiverException