.hgtags @ 884333cfb6fb v1.3.2

Detect *all* cycles during topological sort

Previously the cycle detection was limited to detecting when we hit
a currently-being-visited node during a traversal.  So something like this would
be correctly found:

    A --> B --> C
          ^     |
          |     |
          +-----+

We start at the root (A), go to B, then to C, then to B, and detect that we're
still working on B and signal the error.

But this doesn't find all cycles, because we *start* at the root nodes, and if
a cycle doesn't have any outcropping branches we'll never reach it at all.  For
example:

    A --> B
    ^     |
    |     |
    +-----+

This graph has no roots, so we incorrectly ignore the cycle.

This patch fixes the problem by keeping a count of visited nodes and and making
sure it matches the digraph's size at the end.

Fixes https://github.com/sjl/cl-digraph/issues/4

516585a909d096895330ff634f0eb06c63b4a9f8 v1.0.0
cd7d9aaa93858246761e11ea719433f93a215669 v1.1.0
6f56512ea85afe720f6dc57172b4663f4109f4c2 v1.2.0
8cf220c55f134e63a3c27e560750095ce58e3abb v1.2.1
0434eb58dde39dce2c6f9d99df163e4c80246ebc v1.3.0
e5f60ffb3dc49309d263484a021a04a149e3ac60 v1.3.1