`brief diff` drops detections for uppercase extensions and recursive glob patterns

[abhinavgautam01]

Summary

brief diff can omit languages and tools that are present in the full report when the relevant changed file uses an uppercase extension or matches a recursive ** knowledge-base pattern at more than one directory level.

Examples include R files matched by *.R or **/*.R and Ruby native extensions matched by ext/**/extconf.rb.

Reproduction

In a Git repository with a baseline commit, add these files without committing them:

analysis/nested/model.R
ext/pkg/sub/extconf.rb

Example contents:

x <- 1

require "mkmf"
create_makefile("example")

Compare:

brief --json .
brief diff --json HEAD

The full scan detects R and mkmf. The diff report omits R and mkmf even though both detections are relevant to changed files.

Root cause

There are two problems in detect/filter.go:

1. Changed extensions are stored in lowercase, but extensions extracted from knowledge patterns are looked up without normalization:

ext := pattern[idx+1:]
if changedExts[ext] {
    return true
}

For *.R, the lookup uses .R, while changedExts contains .r.

2. The fallback uses filepath.Match:

if matched, _ := filepath.Match(pattern, f); matched {
    return true
}

Go's filepath.Match does not give ** recursive semantics. A pattern such as ext/**/extconf.rb may match one intermediate segment accidentally, but it does not match deeper paths such as ext/pkg/sub/extconf.rb.

The detection engine already has matchPathPattern, which supports ** across path segments and is used elsewhere in the same filter implementation.

Expected behavior

brief diff should use the same path-pattern semantics as full detection and should handle extension comparisons consistently, regardless of extension case.

Proposed implementation

Normalize the extracted extension:

if changedExts[strings.ToLower(ext)] {
    return true
}

Replace the filepath.Match fallback with the existing matcher:

if matchPathPattern(pattern, f) {
    return true
}

Suggested tests

• Keep R in a diff report for a changed multi-level path ending in .R.
• Keep R Markdown for a changed multi-level path ending in .Rmd.
• Keep mkmf for ext/pkg/sub/extconf.rb.
• Verify ordinary non-recursive patterns retain their existing behavior.