feat: add .shushignore support for flexible file exclusion

- Add .shushignore file support (project root + global ~/.config/.shushignore)
- Support gitignore-style patterns: wildcards (*), directories (dir/), negation (\!pattern)
- Universal integration: works with all processing modes (files, directories, git-aware)
- Smart messaging: explicit ignore messages for direct file access
- Silent skipping: directory traversal automatically skips ignored files
- Enhanced verbose output: distinguishes between ignored vs unsupported files
- Pattern examples: *.tmp, build/, test*.js, \!important.js

internal/ignore/ignore.go

@@ -0,0 +1,230 @@
+package ignore
+
+import (
+	"bufio"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type Ignore struct {
+	patterns []pattern
+}
+
+type pattern struct {
+	original    string
+	normalized  string
+	isNegation  bool
+	isDirectory bool
+}
+
+func New() *Ignore {
+	return &Ignore{
+		patterns: make([]pattern, 0),
+	}
+}
+
+func Load() (*Ignore, error) {
+	ignore := New()
+
+	if globalPath := getGlobalIgnorePath(); globalPath != "" {
+		if err := ignore.loadFromFile(globalPath); err != nil && !os.IsNotExist(err) {
+			return nil, err
+		}
+	}
+
+	if projectPath := getProjectIgnorePath(); projectPath != "" {
+		if err := ignore.loadFromFile(projectPath); err != nil && !os.IsNotExist(err) {
+			return nil, err
+		}
+	}
+
+	return ignore, nil
+}
+
+func (i *Ignore) loadFromFile(path string) error {
+	file, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		i.addPattern(line)
+	}
+
+	return scanner.Err()
+}
+
+func (i *Ignore) addPattern(patternStr string) {
+	p := pattern{
+		original: patternStr,
+	}
+
+	if strings.HasPrefix(patternStr, "!") {
+		p.isNegation = true
+		patternStr = patternStr[1:]
+	}
+
+	if strings.HasSuffix(patternStr, "/") {
+		p.isDirectory = true
+		patternStr = patternStr[:len(patternStr)-1]
+	}
+
+	p.normalized = patternStr
+
+	i.patterns = append(i.patterns, p)
+}
+
+func (i *Ignore) IsIgnored(filePath string) bool {
+	relPath := filepath.Clean(filePath)
+	
+	if strings.HasPrefix(relPath, "./") {
+		relPath = relPath[2:]
+	}
+
+	matched := false
+
+	for _, p := range i.patterns {
+		if i.matchesPattern(relPath, p) {
+			matched = !p.isNegation
+		}
+	}
+
+	return matched
+}
+
+func (i *Ignore) matchesPattern(filePath string, p pattern) bool {
+	if p.isDirectory {
+		if info, err := os.Stat(filePath); err != nil || !info.IsDir() {
+			return false
+		}
+	}
+
+	return i.globMatch(p.normalized, filePath)
+}
+
+func (i *Ignore) globMatch(pattern, path string) bool {
+	if pattern == path {
+		return true
+	}
+
+	if strings.Contains(pattern, "*") {
+		return i.wildcardMatch(pattern, path)
+	}
+
+	if strings.HasSuffix(pattern, "/") {
+		dirPattern := pattern[:len(pattern)-1]
+		return strings.HasPrefix(path, dirPattern+"/") || path == dirPattern
+	}
+
+	if strings.HasPrefix(path, pattern+"/") {
+		return true
+	}
+
+	if filepath.Base(path) == pattern {
+		return true
+	}
+
+	return false
+}
+
+func (i *Ignore) wildcardMatch(pattern, path string) bool {
+	
+	parts := strings.Split(pattern, "*")
+	
+	if len(parts) == 1 {
+		return pattern == path
+	}
+
+	if len(parts[0]) > 0 && !strings.HasPrefix(path, parts[0]) {
+		return false
+	}
+
+	if len(parts[len(parts)-1]) > 0 && !strings.HasSuffix(path, parts[len(parts)-1]) {
+		return false
+	}
+
+	currentPath := path
+	for i := 0; i < len(parts); i++ {
+		part := parts[i]
+		if part == "" {
+			continue
+		}
+
+		if i == 0 {
+			currentPath = currentPath[len(part):]
+			continue
+		}
+
+		if i == len(parts)-1 {
+			break
+		}
+
+		index := strings.Index(currentPath, part)
+		if index == -1 {
+			return false
+		}
+		currentPath = currentPath[index+len(part):]
+	}
+
+	return true
+}
+
+func getGlobalIgnorePath() string {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return ""
+	}
+	return filepath.Join(home, ".config", ".shushignore")
+}
+
+func getProjectIgnorePath() string {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return ""
+	}
+
+	localIgnore := filepath.Join(cwd, ".shushignore")
+	if fileExists(localIgnore) {
+		return localIgnore
+	}
+
+	if gitRoot := findGitRoot(cwd); gitRoot != "" {
+		gitIgnore := filepath.Join(gitRoot, ".shushignore")
+		if fileExists(gitIgnore) && gitIgnore != localIgnore {
+			return gitIgnore
+		}
+	}
+
+	return ""
+}
+
+func findGitRoot(startDir string) string {
+	dir := startDir
+	for {
+		gitDir := filepath.Join(dir, ".git")
+		if fileExists(gitDir) {
+			return dir
+		}
+
+		parent := filepath.Dir(dir)
+		if parent == dir {
+			break
+		}
+		dir = parent
+	}
+	return ""
+}
+
+func fileExists(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
+}

internal/processor/git_processor.go

@@ -63,9 +63,13 @@ func (p *Processor) processGitChanges() error {
 		if IsSupportedFile(change.Path) {
 			supportedChanges = append(supportedChanges, change)
 		} else if p.cli.Verbose {
+			if IsIgnored(change.Path) {
+				fmt.Printf("Skipping ignored file: %s\n", change.Path)
+			} else {
 				fmt.Printf("Skipping unsupported file: %s\n", change.Path)
 			}
 		}
+	}
 
 	if len(supportedChanges) == 0 {
 		fmt.Println("No supported files found to process")

internal/processor/languages.go

@@ -5,6 +5,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/carlosarraes/shush/internal/ignore"
 	"github.com/carlosarraes/shush/internal/types"
 )
 
@@ -152,5 +153,17 @@ func IsSupportedFile(filename string) bool {
 	}
 	ext = strings.TrimPrefix(ext, ".")
 	_, ok := languageMap[ext]
-	return ok
+	if !ok {
+		return false
+	}
+
+	return !IsIgnored(filename)
+}
+
+func IsIgnored(filename string) bool {
+	ignoreChecker, err := ignore.Load()
+	if err != nil {
+		return false
+	}
+	return ignoreChecker.IsIgnored(filename)
 }

internal/processor/processor.go

@@ -40,6 +40,11 @@ func (p *Processor) Process() error {
 		return p.processDirectory(p.cli.Path)
 	}
 
+	if IsIgnored(p.cli.Path) {
+		fmt.Printf("File %s is in .shushignore, ignoring\n", p.cli.Path)
+		return nil
+	}
+
 	return p.processFile(p.cli.Path)
 }