cmd: trailing slash for destination path resolves ambiguity when writ…

…ing to a directory

cmd/minify/README.md

@@ -172,7 +172,9 @@ Minify only javascript files in **src/**:
 $ minify -r -o out/ --match="\.js$" src
 ```
 
-A trailing slash in the source path will copy all files inside the directory, while omitting the trainling slash will copy the directory as well.
+A trailing slash in the source path will copy all files inside the directory, while omitting the trainling slash will copy the directory as well. Both `src/` and `src/*` are equivalent, except that the second case uses input expansion from bash and ignores hidden files starting with a dot.
+
+A trailing slash in the destination path will write a single file into a directory instead of to a file of that name.
 
 ### Concatenate
 When multiple inputs are given and the output is either standard output or a single file, it will concatenate the files together if you use the bundle option.

cmd/minify/main.go

@@ -966,6 +966,9 @@ Next:
 
 // IsDir returns true if the passed string looks like it specifies a directory, false otherwise.
 func IsDir(dir string) bool {
+	if 0 < len(dir) && dir[len(dir)-1] == '/' {
+		return true
+	}
 	info, err := os.Lstat(dir)
 	return err == nil && info.Mode().IsDir() && info.Mode()&os.ModeSymlink == 0
 }