Revert "SI-6039 Harden against irrelevant filesystem details"

This reverts commit b0758f5cb9d966b940933d48bdbb45d17a80de66.

This commit sent startup time through the roof, at least
in some circumstances (it is presumably related to one's
current working directory.)
Merge pull request #2614 from paulp/pr/revert-fs

Revert "SI-6039 Harden against irrelevant filesystem details"