Add support for -xdev

[refi64]

Unfortunately, the nature of this makes it incredibly hard to test for
in CI; not even BFS's massive test suite covers it. That being said,
it's a simple enough addition that the risk it incurs hopefully
shouldn't be too large.

Signed-off-by: Ryan Gonzalez ryan.gonzalez@collabora.com

[codecov]

Codecov Report

Merging #136 (0a8b72f) into main (1517cc0) will decrease coverage by 0.02%.
The diff coverage is 40.00%.

@@            Coverage Diff             @@
##             main     #136      +/-   ##
==========================================
- Coverage   52.52%   52.50%   -0.03%     
==========================================
  Files          23       23              
  Lines        4655     4659       +4     
  Branches     1531     1532       +1     
==========================================
+ Hits         2445     2446       +1     
- Misses       1664     1666       +2     
- Partials      546      547       +1     

Impacted Files	Coverage Δ
src/find/matchers/mod.rs	63.88% <0.00%> (-0.77%)	⬇️
src/find/mod.rs	61.79% <100.00%> (+0.43%)	⬆️

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[sylvestre]

For others:

       -xdev  Don't descend directories on other filesystems.

[tavianator]

not even BFS's massive test suite covers it

Actually ./tests.sh --sudo does cover it, but it needs sudo access. And it's probably not directly useful to uutils since --sudo also tests some bfs-specific extensions. There's no way (yet) to ask for the --sudo tests that are GNU compatible.