fix: replace {} placeholder in -exec utility name

[mvanhorn]

Summary

Fixed -exec to replace {} in the utility_name position, not just in arguments. Previously find -exec {} \; passed the literal string "{}" to Command::new.

Why this matters

Per POSIX (find -exec utility_name [argument ...] ;), a utility_name containing only "{}" should be replaced with the current pathname. GNU find and BSD find both handle this correctly. uutils find failed with "No such file or directory" because {} was never substituted in the executable field.

Repro from #614:

find /usr/bin -name pwd -exec {} -P ';'
# Expected: runs /usr/bin/pwd -P
# Got: Failed to run {}: No such file or directory (os error 2)

Changes

• src/find/matchers/exec.rs: Extracted parse_arg helper from the duplicated split logic. Changed SingleExecMatcher.executable from String to Arg so it undergoes the same {} replacement as arguments. Updated error formatting to use the resolved executable path.

Testing

All 25 existing tests pass. Verified compilation with cargo check and cargo clippy (no warnings). Tested manually with cargo run --bin find -- /usr/bin -name pwd -exec {} -P \;.

Fixes #614

This contribution was developed with AI assistance (Claude Code).

[codecov]

Codecov Report

❌ Patch coverage is 68.75000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.70%. Comparing base (015727f) to head (da847c6).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/find/matchers/exec.rs	68.75%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #647      +/-   ##
==========================================
- Coverage   91.76%   91.70%   -0.06%     
==========================================
  Files          31       31              
  Lines        6203     6207       +4     
  Branches      328      328              
==========================================
  Hits         5692     5692              
- Misses        390      394       +4     
  Partials      121      121              

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[jmr]

What do you do with foo{}bar in the first position? According to POSIX, this is unspecified, but GNU will substitute there.

Also, probably a good idea to add some tests. Claude didn't do that automatically?

[sylvestre]

Indeed, it needs tests

[mvanhorn]

Added a test in da847c6. On the foo{}bar question - the current implementation already handles embedded placeholders via the FileArg(parts) pattern (splits on {} and joins with the pathname), so foo{}bar in any position resolves to foo/path/to/filebar. This matches GNU find behavior.