feat: Initial file walking glob implementation.

glob.go

@@ -1,8 +1,9 @@
 package zglob
 
 import (
+	"fmt"
 	"os"
-	"strings"
+	"path"
 
 	"github.com/gobwas/glob"
 	"github.com/spf13/afero"
@@ -14,14 +15,78 @@ func Glob(pattern string) ([]string, error) {
 
 func GlobWithFs(fs afero.Fs, pattern string) ([]string, error) {
 	var matches []string
-	g, err := glob.Compile(strings.TrimPrefix(pattern, "./"), '/')
+
+	matcher, err := glob.Compile(pattern)
 	if err != nil {
 		return matches, err
 	}
-	return matches, afero.Walk(fs, ".", func(path string, info os.FileInfo, err error) error {
- 		if g.Match(path) {
- 			matches = append(matches, path)
- 		}
- 		return nil
- 	})
+
+	prefix, err := staticPrefix(pattern)
+	if err != nil {
+		return nil, fmt.Errorf("determine static prefix: %w", err)
+	}
+
+	prefixInfo, err := os.Stat(prefix)
+	if os.IsNotExist(err) {
+		// if the prefix does not exist, the whole
+		// glob pattern won't match anything
+		return []string{}, nil
+	} else if err != nil {
+		return nil, fmt.Errorf("stat prefix: %w", err)
+	}
+
+	if !prefixInfo.IsDir() {
+		// if the prefix is a file, it either has to be
+		// the only match, or nothing matches at all
+		if matcher.Match(prefix) {
+			return []string{prefix}, nil
+		}
+
+		return []string{}, nil
+	}
+
+	return matches, afero.Walk(fs, prefix, func(currentPath string, info os.FileInfo,
+		err error) error {
+		if err != nil {
+			return err
+		}
+
+		if !matcher.Match(info.Name()) {
+			return nil
+		}
+
+		if info.IsDir() {
+			// a direct match on a directory implies that all files inside match
+			filesInDir, err := filesInDirectory(fs, path.Join(currentPath, info.Name()))
+			if err != nil {
+				return err
+			}
+
+			matches = append(matches, filesInDir...)
+		} else {
+			matches = append(matches, path.Join(currentPath, info.Name()))
+		}
+
+		return nil
+	})
+}
+
+func filesInDirectory(fs afero.Fs, dir string) ([]string, error) {
+	files := []string{}
+
+	err := afero.Walk(fs, dir, func(currentPath string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if info.IsDir() {
+			return nil
+		}
+
+		files = append(files, path.Join(currentPath, info.Name()))
+
+		return nil
+	})
+
+	return files, err
 }

prefix.go

@@ -10,6 +10,8 @@ import (
 	"github.com/gobwas/glob/syntax/lexer"
 )
 
+// staticPrefix returns the filepath up to the
+// first path element that contains a wildcard.
 func staticPrefix(pattern string) (string, error) {
 	parts := strings.Split(pattern, string(filepath.Separator))