Only recursively expand .thrift files (#64)

Otherwise, we would attempt to parse non-Thrift nested within the
directory hierarchy.

Author: jparise

README.md

@@ -10,7 +10,7 @@ command line tool (`thriftcheck`).
 the command line:
 
 ```
-usage: thriftcheck [options] [file ...]
+usage: thriftcheck [options] [path ...]
   -I, --include value
     	include path (can be specified multiple times)
   -c, --config string
@@ -29,8 +29,11 @@ usage: thriftcheck [options] [file ...]
     	print the version and exit
 ```
 
-You can lint from standard input by passing `-` as the sole filename. You can
-also use `--stdin-name` to customize the filename used in output messages.
+You can pass a list of filenames or directory paths. Directories will be
+expanded recursively to include all nested `.thrift` files.
+
+You also can lint from standard input by passing `-` as the sole filename. You
+can also use `--stdin-name` to customize the filename used in output messages.
 
 ```sh
 $ thriftlint --stdin-name filename.thrift - < filename.thrift
@@ -43,12 +46,6 @@ file.thrift:1:1: error: "py" namespace must match "^idl\\." (namespace.pattern)
 file.thrift:3:1: error: unable to find include path for "bar.thrift" (include.path)
 ```
 
-You can also directly use the path of a directory to check all the Thrift files within the folder.
-
-```sh
-$ thriftlint ./testdata
-```
-
 If you only want errors (and not warnings) to be reported, you can use the
 `--errors-only` command line option.
 

cmd/main.go

@@ -87,7 +87,7 @@ var (
 func init() {
 	flag.Var(&includes, "I", "include path (can be specified multiple times)")
 	flag.Usage = func() {
-		fmt.Fprintf(flag.CommandLine.Output(), "usage: thriftcheck [options] [file ...]\n")
+		fmt.Fprintf(flag.CommandLine.Output(), "usage: thriftcheck [options] [path ...]\n")
 		getopt.PrintDefaults()
 	}
 	getopt.Aliases(
@@ -148,7 +148,7 @@ func expandPaths(paths []string) ([]string, error) {
 				return err
 			}
 
-			if !info.IsDir() {
+			if !info.IsDir() && filepath.Ext(path) == ".thrift" {
 				filenames = append(filenames, path)
 			}