index: make capacity argument to nt_init be measured in revisions

The nodetree's internal capacity field is measures in nodetree nodes,
which is not something the caller should have to know about.

Differential Revision: https://phab.mercurial-scm.org/D4166

mercurial/cext/revlog.c

@@ -1065,7 +1065,9 b' static int nt_delete_node(nodetree *self'
 static int nt_init(nodetree *self, indexObject *index, unsigned capacity)
 {
 	self->index = index;
-	self->capacity = capacity;
+	/* The input capacity is in terms of revisions, while the field is in
+	 * terms of nodetree nodes. */
+	self->capacity = (capacity < 4 ? 4 : capacity / 2);
 	self->depth = 0;
 	self->splits = 0;
 	if ((size_t)self->capacity > INT_MAX / sizeof(nodetreenode)) {
@@ -1141,8 +1143,7 b' static int index_init_nt(indexObject *se'
 			PyErr_NoMemory();
 			return -1;
 		}
-		unsigned capacity = (self->raw_length < 4 ? 4 : (int)self->raw_length / 2);
-		if (nt_init(self->nt, self, capacity) == -1) {
+		if (nt_init(self->nt, self, self->raw_length) == -1) {
 			PyMem_Free(self->nt);
 			self->nt = NULL;
 			return -1;