fix: forward windows option to basename in matchBase

[chatman-media]

What

picomatch.matchBase no longer honors the windows option, so backslash-separated paths are not split into segments when matching a basename pattern with { matchBase: true, windows: true }.

const picomatch = require('picomatch');

picomatch.isMatch('a\\b\\c\\foo.md', '*.md', { matchBase: true, windows: true });
//=> false  (expected: true)

picomatch.matchBase('foo\\bar.js', '*.js', { windows: true });
//=> false  (expected: true)

Forward-slash paths work as expected; only backslash separators are affected.

Why

When windows: true, the parser builds a regex whose path-segment class excludes both separators ([^\\/]), so a multi-segment backslash path like a\b\c\foo.md can't match a single-segment pattern like *.md directly. Matching then falls back to picomatch.matchBase, which is supposed to test the basename of the input.

picomatch.test still passes the posix/windows flag to matchBase:

match = picomatch.matchBase(input, regex, options, posix);

but in #64 (commit 2f25761, "Remove automatic windows detection") matchBase was changed from Node's path.basename to the internal utils.basename, and in the process:

• the trailing posix parameter was dropped from the signature, and
• utils.basename(input) was called without the { windows } flag.

utils.basename already supports { windows: true } (and is covered by tests in test/regex-features.js), so without the flag it only ever splits on /. For a backslash path it returns the whole string, which then fails the regex.

Fix

Restore the posix parameter (defaulting to options.windows, mirroring how picomatch.test derives it) and forward it to utils.basename:

picomatch.matchBase = (input, glob, options, posix = options && options.windows) => {
  const regex = glob instanceof RegExp ? glob : picomatch.makeRe(glob, options);
  return regex.test(utils.basename(input, { windows: posix }));
};

Minimal change; no behavior change for POSIX paths.

Tests

Added cases under options.matchBase in test/options.js covering backslash-separated paths with { matchBase: true, windows: true } and a direct matchBase(..., { windows: true }) call. Verified they fail without the fix and pass with it. Full suite green (npm run mocha → 1977 passing) and npm run lint clean.