parsers: rewrite index_ancestors() in terms of index_commonancestorsheads()

parsers: rewrite index_ancestors() in terms of index_commonancestorsheads()

The first 80% of index_ancestors() is identical to
index_commonancestorsheads(), so just call that function instead.

--- a/mercurial/parsers.c	Thu Jan 22 11:09:34 2015 -0500
+++ b/mercurial/parsers.c	Fri Jan 23 14:09:49 2015 -0800
@@ -1676,108 +1676,6 @@
 }
 
 /*
- * Given a (possibly overlapping) set of revs, return the greatest
- * common ancestors: those with the longest path to the root.
- */
-static PyObject *index_ancestors(indexObject *self, PyObject *args)
-{
-	PyObject *ret = NULL, *gca = NULL;
-	Py_ssize_t argcount, i, len;
-	bitmask repeat = 0;
-	int revcount = 0;
-	int *revs;
-
-	argcount = PySequence_Length(args);
-	revs = malloc(argcount * sizeof(*revs));
-	if (argcount > 0 && revs == NULL)
-		return PyErr_NoMemory();
-	len = index_length(self) - 1;
-
-	for (i = 0; i < argcount; i++) {
-		static const int capacity = 24;
-		PyObject *obj = PySequence_GetItem(args, i);
-		bitmask x;
-		long val;
-
-		if (!PyInt_Check(obj)) {
-			PyErr_SetString(PyExc_TypeError,
-					"arguments must all be ints");
-			Py_DECREF(obj);
-			goto bail;
-		}
-		val = PyInt_AsLong(obj);
-		Py_DECREF(obj);
-		if (val == -1) {
-			ret = PyList_New(0);
-			goto done;
-		}
-		if (val < 0 || val >= len) {
-			PyErr_SetString(PyExc_IndexError,
-					"index out of range");
-			goto bail;
-		}
-		/* this cheesy bloom filter lets us avoid some more
-		 * expensive duplicate checks in the common set-is-disjoint
-		 * case */
-		x = 1ull << (val & 0x3f);
-		if (repeat & x) {
-			int k;
-			for (k = 0; k < revcount; k++) {
-				if (val == revs[k])
-					goto duplicate;
-			}
-		}
-		else repeat |= x;
-		if (revcount >= capacity) {
-			PyErr_Format(PyExc_OverflowError,
-				     "bitset size (%d) > capacity (%d)",
-				     revcount, capacity);
-			goto bail;
-		}
-		revs[revcount++] = (int)val;
-	duplicate:;
-	}
-
-	if (revcount == 0) {
-		ret = PyList_New(0);
-		goto done;
-	}
-	if (revcount == 1) {
-		PyObject *obj;
-		ret = PyList_New(1);
-		if (ret == NULL)
-			goto bail;
-		obj = PyInt_FromLong(revs[0]);
-		if (obj == NULL)
-			goto bail;
-		PyList_SET_ITEM(ret, 0, obj);
-		goto done;
-	}
-
-	gca = find_gca_candidates(self, revs, revcount);
-	if (gca == NULL)
-		goto bail;
-
-	if (PyList_GET_SIZE(gca) <= 1) {
-		ret = gca;
-		Py_INCREF(gca);
-	}
-	else ret = find_deepest(self, gca);
-
-done:
-	free(revs);
-	Py_XDECREF(gca);
-
-	return ret;
-
-bail:
-	free(revs);
-	Py_XDECREF(gca);
-	Py_XDECREF(ret);
-	return NULL;
-}
-
-/*
  * Given a (possibly overlapping) set of revs, return all the
  * common ancestors heads: heads(::args[0] and ::a[1] and ...)
  */
@@ -1871,6 +1769,24 @@
 }
 
 /*
+ * Given a (possibly overlapping) set of revs, return the greatest
+ * common ancestors: those with the longest path to the root.
+ */
+static PyObject *index_ancestors(indexObject *self, PyObject *args)
+{
+	PyObject *gca = index_commonancestorsheads(self, args);
+	if (gca == NULL)
+		return NULL;
+
+	if (PyList_GET_SIZE(gca) <= 1) {
+		Py_INCREF(gca);
+		return gca;
+	}
+
+	return find_deepest(self, gca);
+}
+
+/*
  * Invalidate any trie entries introduced by added revs.
  */
 static void nt_invalidate_added(indexObject *self, Py_ssize_t start)