[Fix] properly determine length of rootValids for engine in isSame comparison

[travi]

in attempting to understand why our newly added ls-engines checks were failing for semantic-release/npm#402 and semantic-release/github#412, i tracked down that the graphValids and rootValids were the same lists, but not being reported as such.

i havent tracked down how to cover this gap in the tests yet, but wanted to get this much out here before calling it a (late) night. i'm happy to help get a test in place for this with a little guidance.

[ljharb]

woof, that’s an obvious bug. I’ll take a look this weekend and see if i can come up with tests.

[codecov]

Codecov Report

Merging #23 (c0d5356) into main (b91f667) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #23   +/-   ##
=======================================
  Coverage   82.35%   82.35%           
=======================================
  Files           5        5           
  Lines          85       85           
  Branches       26       26           
=======================================
  Hits           70       70           
  Misses         15       15           

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[travi]

I’ll take a look this weekend and see if i can come up with tests.

thanks for taking a look. having looked through the test suite, it does seem like you would be better suited to address the tests on this one, but let me know if it would be worth me digging deeper.

[ljharb]

I'll definitely take a crack at it before asking you to do more work :-) thanks!

[ljharb]

Thanks! I added tests, and will land and release this shortly.

[travi]

just getting back from vacation, so this was a great thing to come back to. thanks so much for taking care of this!