Fix rglob TypeError when a blob and a directory share a name (#431)

[pjbull]

Fixes #431.

Problem

CloudPath.rglob crashed with TypeError: 'NoneType' object is not subscriptable when a bucket contained both a blob and a "directory" prefix sharing the same name — a layout cloud object stores allow but local filesystems do not. The reporter and a second user hit this on GCS; the same code path is used for every backend.

The crash came from _build_subtree in cloudpath.py. The recursive _build_tree helper writes None for a file leaf and a nested defaultdict for a directory. When a file entry was processed first at path output, then a deeper entry like output/13655/0/file1.json arrived, the helper did trunk[branch][next_branch] on the None leaf and crashed. The reverse case — directory first, file with the same name second — overwrote the populated subtree with None, silently losing descendants.

Fix

_build_tree now treats a file leaf and a directory subtree as mergeable at the same path:

• If a recursion needs to descend into a branch that's currently a None leaf, promote it to a Tree() before recursing.
• If a leaf write would clobber an existing subtree, keep the subtree (descendants matter more than the leaf marker).
• If a directory entry arrives for a path that already has a subtree, reuse it rather than overwriting.

This also covers the reverse ordering, where the directory entry for output/13655/0 is listed after output/13655/0/file1.json and previously wiped out the file.

Test

Added test_rglob_file_and_dir_same_name in tests/test_cloudpath_file_io.py. It monkeypatches client._list_dir to emit a blob and a directory at the same path (which the local-FS-backed mocks can't represent naturally), then asserts rglob("*") returns the descendants without raising. Runs against all 10 rigs.

Verification

• make lint clean (black, flake8, mypy)
• make test — 1102 passed, 7 skipped
• New regression test passes on all rigs (S3, GS, Azure, local variants, HTTP)

[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.6%. Comparing base (9d5fa70) to head (15e4c61).

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #577     +/-   ##
========================================
- Coverage    94.3%   93.6%   -0.8%     
========================================
  Files          28      28             
  Lines        2267    2272      +5     
========================================
- Hits         2140    2128     -12     
- Misses        127     144     +17     

Files with missing lines	Coverage Δ
cloudpathlib/cloudpath.py	95.2% <100.0%> (-0.3%)	⬇️

... and 1 file with indirect coverage changes

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