[rfile] ListKeys: don't include the root directory itself in the listing

[silverweed]

This Pull request:

changes the behavior of RFile::ListKeys to exclude the root directory itself from the list of returned keyInfos.

Previously ListKeys("a", kListDirs) would return (e.g.) { "a", "a/b", "a/c", "a/d" }; now it only returns { "a/b", "a/c", "a/d" }.

Rationale: you generally don't care about the root dir in the listing, since you already know it's there.

[github-actions]

Test Results

    21 files      21 suites   3d 10h 18m 53s ⏱️
 3 863 tests  3 802 ✅   0 💤 61 ❌
72 810 runs  72 642 ✅ 107 💤 61 ❌

For more details on these failures, see this check.

Results for commit ef1c2d7.