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 70.58824% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.78%. Comparing base (a65160f) to head (4675963).

Files with missing lines	Patch %	Lines
src/find/matchers/exec.rs	70.58%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #647      +/-   ##
==========================================
- Coverage   91.83%   91.78%   -0.06%     
==========================================
  Files          31       31              
  Lines        6408     6413       +5     
  Branches      338      338              
==========================================
+ Hits         5885     5886       +1     
- Misses        397      401       +4     
  Partials      126      126              

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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.

[sylvestre]

sorry, it needs to be rebased :/

[mvanhorn]

Appreciate the merge @sylvestre. Nice to have {} substitution in the utility_name position matching POSIX and GNU find now.