[dajiaohuang]

Summary

Preserve ancestor .gitignore rules when entering a directory with its own .gitignore. Check the ignore stack from the closest directory outward, stopping at the first matching rule so that a child's explicit whitelist still takes precedence.

Reproduction

With *.log in the root .gitignore and *.tmp in nested/.gitignore, ambs needle . currently searches nested/ignored.log. Likewise, ambr --no-interactive needle replacement . rewrites it, despite the inherited ignore pattern. Merely adding an unrelated nested .gitignore should not stop the root pattern from applying.

Validation

• Added CLI regression tests for both search and replacement, including child whitelist precedence and unchanged ignored-file contents. Both fail on the unchanged base and pass with this change.
• All 9 existing library tests and the 2 new integration tests pass on Windows x86-64 and Linux x86-64 (test executables run from isolated fixture directories).
• Additional isolated CLI checks cover literal/regex search and replacement, captures, file-based keywords/replacements, Unicode, binary/VCS filtering, large-file search, timestamp preservation, and Linux config overrides; interactive yes/no/all replacement also checked on Linux.
• cargo fmt --all -- --check and git diff --check pass.

No macOS or ARM64 validation was run.