find: reject a signed -maxdepth/-mindepth value to match GNU

[AlejandroCoronadoN]

Problem

-maxdepth/-mindepth accepted a +-signed value that GNU rejects:

$ find dir -maxdepth +1     # uutils: runs normally (parsed as 1)
$ gfind dir -maxdepth +1
find: Expected a positive decimal integer argument to -maxdepth, but got '+1'

Rust's usize::from_str accepts a leading +, so convert_arg_to_number let
it through, which is inconsistent with the function's own "positive decimal
integer" error message.

Fix

Only accept plain decimal digits.

Verification

Compared against GNU findutils (gfind) for -maxdepth and -mindepth over
1, +1, -1, +2, 0, 2; exit codes match in every case. Added a unit
test; cargo test --lib passes and cargo fmt / cargo clippy are clean.

[codspeed-hq]

Merging this PR will not alter performance

✅ 20 untouched benchmarks

---

_{Comparing AlejandroCoronadoN:fix-maxdepth-signed (0f7a2da) with main (1acf40a)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.27%. Comparing base (1acf40a) to head (0f7a2da).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #835      +/-   ##
==========================================
+ Coverage   92.22%   92.27%   +0.05%     
==========================================
  Files          35       35              
  Lines        7435     7435              
  Branches      386      386              
==========================================
+ Hits         6857     6861       +4     
+ Misses        437      433       -4     
  Partials      141      141              

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[github-actions]

Commit 2c18ead has test result changes:

GNU findutils testsuite:

Test results comparison:
  Current:   TOTAL: 495 / PASSED: 421 / FAILED: 73 / SKIPPED: 1
  Reference: TOTAL: 495 / PASSED: 417 / FAILED: 77 / SKIPPED: 1

Changes from main branch:
  TOTAL: +0
  PASSED: +4
  FAILED: -4

Test improvements (4):
  + mindepth-badarg.new-O0
  + mindepth-badarg.new-O1
  + mindepth-badarg.new-O2
  + mindepth-badarg.new-O3

bfs testsuite:

Test results comparison:
  Current:   TOTAL: 313 / PASSED: 266 / FAILED: 41 / SKIPPED: 6
  Reference: TOTAL: 313 / PASSED: 267 / FAILED: 40 / SKIPPED: 6

Changes from main branch:
  TOTAL: +0
  PASSED: -1
  FAILED: +1

New test failures (1):
  - gnu/files0_from_ok

[sylvestre]

please add a test_find.rs

[AlejandroCoronadoN]

Done, added an integration test in test_find.rs for the signed -maxdepth/-mindepth case.

[github-actions]

Commit e056014 has test result changes:

GNU findutils testsuite:

Test results comparison:
  Current:   TOTAL: 495 / PASSED: 424 / FAILED: 70 / SKIPPED: 1
  Reference: TOTAL: 495 / PASSED: 420 / FAILED: 74 / SKIPPED: 1

Changes from main branch:
  TOTAL: +0
  PASSED: +4
  FAILED: -4

Test improvements (4):
  + mindepth-badarg.new-O0
  + mindepth-badarg.new-O1
  + mindepth-badarg.new-O2
  + mindepth-badarg.new-O3

bfs testsuite:

Test results comparison:
  Current:   TOTAL: 315 / PASSED: 267 / FAILED: 42 / SKIPPED: 6
  Reference: TOTAL: 314 / PASSED: 266 / FAILED: 42 / SKIPPED: 6

Changes from main branch:
  TOTAL: +1
  PASSED: +1
  FAILED: +0

New test failures (1):
  - gnu/okdir_path_relative

Test improvements (1):
  + gnu/okdir_path_empty

[github-actions]

Commit f9fbd6e has test result changes:

GNU findutils testsuite:

Test results comparison:
  Current:   TOTAL: 495 / PASSED: 425 / FAILED: 69 / SKIPPED: 1
  Reference: TOTAL: 495 / PASSED: 421 / FAILED: 73 / SKIPPED: 1

Changes from main branch:
  TOTAL: +0
  PASSED: +4
  FAILED: -4

Test improvements (4):
  + mindepth-badarg.new-O0
  + mindepth-badarg.new-O1
  + mindepth-badarg.new-O2
  + mindepth-badarg.new-O3

bfs testsuite:

Test results comparison:
  Current:   TOTAL: 314 / PASSED: 267 / FAILED: 41 / SKIPPED: 6
  Reference: TOTAL: 313 / PASSED: 267 / FAILED: 40 / SKIPPED: 6

Changes from main branch:
  TOTAL: +1
  PASSED: +0
  FAILED: +1

New test failures (1):
  - gnu/okdir_path_relative

[sylvestre]

a bunch of jobs have been failing

[AlejandroCoronadoN]

The failing jobs were from a stale base; rebased the branch on the latest main. fmt, clippy and the tests pass locally now.

[github-actions]

Commit 0f7a2da has test result changes:

GNU findutils testsuite:

Test results comparison:
  Current:   TOTAL: 495 / PASSED: 425 / FAILED: 69 / SKIPPED: 1
  Reference: TOTAL: 495 / PASSED: 421 / FAILED: 73 / SKIPPED: 1

Changes from main branch:
  TOTAL: +0
  PASSED: +4
  FAILED: -4

Test improvements (4):
  + mindepth-badarg.new-O0
  + mindepth-badarg.new-O1
  + mindepth-badarg.new-O2
  + mindepth-badarg.new-O3