Add -I include option, and some usage examples

main.go

@@ -47,9 +47,25 @@ to a regular expression to make that specific expression case insensitive.
 
 Files and directories can be excluded with the -x option. This supports bash-style
 globs with '*', '?', '[a-z]', '{this,that}', or '/**/' to match zero or more
-directories. By default, .git and vim swap files are ignored. Symlinks named on
-the command line are followed, but by default symlinks are not followed when
-recursing into directories. -L allows them to be dereferenced.`,
+directories. By default, .git and vim swap files are ignored. Similarly, -I
+filters files to include. Examples:
+
+	# ignore files/dirs with .js or .css suffix
+	gg -x '*.js' -x '*.css' pattern
+
+	# only match files with .go suffix (any subdir)
+	gg -I '*.go' pattern
+
+	# only match files whose parent dir is "stuff", but ignore "foo" subdir
+	gg -x ./foo -I 'stuff/*' pattern
+
+	# only match .js files with a directory "things" in the path, but ignore
+	# .min.js (e.g. will match "foo/things/bar/my.js")
+	gg -I 'things/**/*.js' -x '*.min.js' pattern
+
+Symlinks named on the command line are followed, but by default symlinks are
+not followed when recursing into directories. -L allows them to be
+dereferenced.`,
 
 	RunE: run,
 }
@@ -60,6 +76,7 @@ var (
 	searchFixed    []string
 	searchPath     []string
 	excludeList    []string
+	includeList    []string
 	ignoreCase     bool
 	noColour       bool
 	binaryFile     notPlainTextFlag
@@ -78,6 +95,7 @@ func init() {
 	rootCmd.Flags().StringSliceVarP(&searchRegexp, "grep", "e", nil, "pattern to match (regular expression)")
 	rootCmd.Flags().StringSliceVarP(&searchFixed, "fixed", "Q", nil, "pattern to match (fixed string)")
 	rootCmd.Flags().StringSliceVarP(&excludeList, "exclude", "x", []string{".git", ".*.swp"}, "files/directories to exclude")
+	rootCmd.Flags().StringSliceVarP(&includeList, "include", "I", nil, "files/directories to include")
 	rootCmd.Flags().BoolVarP(&ignoreCase, "ignore-case", "i", false, "make all searches case insensitive")
 	rootCmd.Flags().BoolVarP(&noColour, "no-colour", "C", false, "disable colour output")
 	rootCmd.Flags().Var(&binaryFile, "binary", "what to do with binary files")
@@ -86,12 +104,10 @@ func init() {
 }
 
 func run(c *cobra.Command, args []string) error {
-	// if we got past argument passing, then returned errors are runtime
-	// things (like file not found) that shouldn't trigger a usage message.
-	c.SilenceUsage = true
-
 	display = NewDisplay(noColour)
 
+	// if no -e or -Q flag is passed, then the first arg is taken to be
+	// the pattern to match
 	if len(searchRegexp) == 0 && len(searchFixed) == 0 {
 		if len(args) == 0 {
 			return errors.New("no pattern specified")
@@ -100,11 +116,18 @@ func run(c *cobra.Command, args []string) error {
 		args = args[1:]
 	}
 
+	// remaining arguments are treated as search paths; an empty list is
+	// taken to mean the CWD
 	searchPath = args
 	if len(searchPath) == 0 {
 		searchPath = append(searchPath, ".")
 	}
 
+	// if we got past argument passing, then returned errors are runtime
+	// things (like file not found) that shouldn't trigger a usage message.
+	c.SilenceUsage = true
+
+	// for -x and -I, an undecorated pattern is treated as a suffix match
 	for i, x := range excludeList {
 		if !strings.HasPrefix(x, "**/") && !strings.HasPrefix(x, "./") {
 			x = "**/" + x
@@ -114,7 +137,17 @@ func run(c *cobra.Command, args []string) error {
 			return fmt.Errorf("invalid exclude pattern %q", x)
 		}
 	}
+	for i, x := range includeList {
+		if !strings.HasPrefix(x, "**/") && !strings.HasPrefix(x, "./") {
+			x = "**/" + x
+			includeList[i] = x
+		}
+		if !doublestar.ValidatePattern(x) {
+			return fmt.Errorf("invalid include pattern %q", x)
+		}
+	}
 
+	// compile regular expressions for matching
 	for _, r := range searchRegexp {
 		if ignoreCase {
 			r = "(?i)" + r
@@ -125,7 +158,6 @@ func run(c *cobra.Command, args []string) error {
 		}
 		regexps = append(regexps, re)
 	}
-
 	for _, r := range searchFixed {
 		r = regexp.QuoteMeta(r)
 		if ignoreCase {
@@ -137,6 +169,7 @@ func run(c *cobra.Command, args []string) error {
 		regexps = append(regexps, re)
 	}
 
+	// search over named paths
 	var errs []error
 	for _, path := range searchPath {
 		if err := search(path, true); err != nil {
@@ -154,17 +187,11 @@ func recurse(path string) error {
 	}
 
 	var errs []error
-NextFile:
 	for _, de := range d {
-		name := de.Name()
-		fullPath := filepath.Join(path, name)
-
-		for _, x := range excludeList {
-			if exclude, _ := doublestar.Match(x, fullPath); exclude {
-				continue NextFile
-			}
+		fullPath := filepath.Join(path, de.Name())
+		if !shouldSearch(fullPath, de.IsDir()) {
+			continue
 		}
-
 		if err := search(fullPath, followSymlinks); err != nil {
 			errs = append(errs, err)
 		}
@@ -172,6 +199,40 @@ NextFile:
 	return errors.Join(errs...)
 }
 
+// shouldSearch matches the full path of the file against the include and
+// exclude lists, returning true if we should consider the file/directory for
+// searching and false if not.
+func shouldSearch(fullPath string, isDir bool) bool {
+	// process the exclude list first
+	for _, x := range excludeList {
+		if exclude, _ := doublestar.Match(x, fullPath); exclude {
+			return false
+		}
+	}
+
+	// if the include list is empty, everything is included
+	if len(includeList) == 0 {
+		return true
+	}
+
+	for _, x := range includeList {
+		match, _ := doublestar.Match(x, fullPath)
+		fmt.Printf("[DEBUG] x=%q fullPath=%q isDir=%t match=%t\n", x, fullPath, isDir, match)
+
+		// if it's a directory, and we have at least one recursive
+		// matcher, then search
+		if isDir && strings.HasPrefix(x, "**/") {
+			return true
+		}
+
+		if include, _ := doublestar.Match(x, fullPath); include {
+			return true
+		}
+	}
+
+	return false
+}
+
 func search(path string, deref bool) error {
 	var (
 		st  os.FileInfo