support running a sequence of Maven builds in dependency order

The new "koji chainmaven" command allows Maven builds to be run in depdencency order,
without needing to wait for repo regens.  A config file specifies the parameters and
dependencies for each build in the sequence.  Each build is launched as soon as all
dependent builds are complete, and is able to reference the output of all of its
dependencies.  If the build source URL and parameters match the latest build of the
same package in the destination tag, the build will not be re-run.

koji/util.py

@@ -133,6 +133,14 @@ def dslice(dict, keys, strict=True):
             ret[key] = dict[key]
     return ret
 
+def dslice_ex(dict, keys, strict=True):
+    """Returns a new dictionary with only the specified keys removed"""
+    ret = dict.copy()
+    for key in keys:
+        if strict or ret.has_key(key):
+            del ret[key]
+    return ret
+
 def call_with_argcheck(func, args, kwargs={}):
     """Call function, raising ParameterError if args do not match"""
     try:
@@ -429,3 +437,24 @@ class adler32_constructor(object):
 
     digest_size = 4
     block_size = 1      #I think
+
+def tsort(parts):
+    """Given a partial ordering, return a totally ordered list.
+
+    part is a dict of partial orderings.  Each value is a set,
+    which the key depends on.
+
+    The return value is a list of sets, each of which has only
+    dependencies on items in previous entries in the list."""
+    parts = parts.copy()
+    result = []
+    while True:
+        level = set([name for name, deps in parts.iteritems() if not deps])
+        if not level:
+            break
+        result.append(level)
+        parts = dict([(name, deps - level) for name, deps in parts.iteritems()
+                      if name not in level])
+    if parts:
+        raise ValueError, 'total ordering not possible'
+    return result