[PATCH] New SymbolTransforms

Hi,

Here are three new SymbolTransforms I've written.  I hope these are
generic and useful enough to be accepted into cvs2svn.

* SubtreeSymbolTransform

    This wraps another SymbolTransform and limits it to only apply
    within a certain directory.  E.g.:

        SubtreeSymbolTransform('myrepo/some_module',
                RegexpSymbolTransform('.*-br', r'\1-branch'))

    Will only do the regexp transform within the specified module.

    This allows more powerful transforms than the existing
    SubtreeSymbolMapper.

* IgnoreTagsExceptSpecifiedOnesSymbolTransform

    Sometimes, you want to ignore most -- but not all -- CVS tags.
    That's what this does.  Typical usage:

        IgnoreTagsExceptSpecifiedOnesSymbolTransform([
            'release-52', 'release-53'])

* ExcludeBranchesSymbolTransform

    I want to ignore all branches in certain modules, but keep those
    branches in other modules.  This class renames all branches to
    "cvs2svn-excluded-br-.*", and then I can exclude those branches
    later with a StrategyRule.  This class can be wrapped in a
    SubtreeSymbolTransform to restrict it to a single CVS module.
    E.g.:

        SubtreeSymbolTransform('myrepo/never_branch_module',
                ExcludeBranchesSymbolTransform())

    This class makes sure it doesn't exclude any tags.

I'd welcome any feedback or review of this patch.

Kind regards,

Jon

P.S. It looks like SymbolTransforms have to be defined in the
cvs2svn core - I originally tried to define these in my options.py
file, but that fails with a pickle error.


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Index: cvs2svn_lib/symbol_transform.py
===================================================================
--- cvs2svn_lib/symbol_transform.py	(revision 5065)
+++ cvs2svn_lib/symbol_transform.py	(working copy)
@@ -234,3 +234,74 @@
       return symbol_name
 
 
+class SubtreeSymbolTransform(SymbolTransform):
+  '''A wrapper around any other SymbolTransform, that limits it to a
+  specified subtree.'''
+
+  def __init__(self, cvs_path, inner_symbol_transform):
+    '''Constructor.
+    CVS_PATH is the path in the repository.
+    INNER_SYMBOL_TRANSFORM is the SymbolTransform to wrap.'''
+
+    assert type(cvs_path) == str
+    self.__subtree = os.path.normcase(os.path.normpath(cvs_path))
+    self.__inner = inner_symbol_transform
+
+  def __does_rule_apply_to(self, cvs_file):
+    cvs_path = os.path.normcase(os.path.normpath(cvs_file.filename))
+    while cvs_path != self.__subtree:
+      new_cvs_path = os.path.dirname(cvs_path)
+      if new_cvs_path == cvs_path:
+        return False
+      cvs_path = new_cvs_path
+    return True
+
+  def transform(self, cvs_file, symbol_name, revision):
+    if self.__does_rule_apply_to(cvs_file):
+      return self.__inner.transform(cvs_file, symbol_name, revision)
+    else:
+      # Rule does not apply to that path; return symbol name unaltered.
+      return symbol_name
+
+
+class IgnoreTagsExceptSpecifiedOnesSymbolTransform(SymbolTransform):
+  """Ignores tag symbols that are not in a list."""
+
+  def __init__(self, tags_to_keep):
+    """Create an SymbolTransform that ignores tag symbols that are
+    not in the tags_to_keep list.
+
+    TAGS_TO_KEEP is an iterable returning strings."""
+
+    self.__tags_to_keep = frozenset(tags_to_keep)
+    for s in self.__tags_to_keep:
+      assert type(s) == str
+
+  def transform(self, cvs_file, symbol_name, revision):
+    if revision.count('.') % 2 == 0:
+      # SymbolTransforms cannot exclude branches
+      return symbol_name
+    elif symbol_name in self.__tags_to_keep:
+      # It's a tag that was explicitly included
+      return symbol_name
+    else:
+      # It's a tag that should be excluded
+      return None
+
+
+class ExcludeBranchesSymbolTransform(SymbolTransform):
+  """Exclude all branch symbols.
+  
+  Note that branches cannot really be filtered out by a
+  SymbolTransform, so they will be renamed to branches
+  of the form "cvs2svn-excluded-br-[original name]".  You
+  can then exclude those branches at the SymbolStrategy stage.
+  """
+
+  def transform(self, cvs_file, symbol_name, revision):
+    if revision.count('.') % 2 != 0:
+      # Tag, leave it.
+      return symbol_name
+    else:
+      # Branch, so exclude it
+      return 'cvs2svn-excluded-br-' + symbol_name