Create a glob package.

pkg/glob/README.md

+`glob` is a file and directory globbing library that supports both checking
+whether a path matches a glob and listing all entities that match a glob.
+
+A "glob" is a pattern designed specifically to match files and directories. Most
+shells support globs natively.
+
+## Usage
+
+To construct a glob, just use `new Glob()`. As with `RegExp`s, it's a good idea
+to keep around a glob if you'll be using it more than once so that it doesn't
+have to be compiled over and over. You can check whether a path matches the glob
+using `Glob.matches()`:
+
+```dart
+import 'package:glob/glob.dart';
+
+final dartFile = new Glob("**.dart");
+
+// Print all command-line arguments that are Dart files.
+void main(List<String> arguments) {
+  for (var argument in arguments) {
+    if (dartFile.matches(argument)) print(argument);
+  }
+}
+```
+
+You can also list all files that match a glob using `Glob.list()` or
+`Glob.listSync()`:
+
+```dart
+import 'package:glob/glob.dart';
+
+final dartFile = new Glob("**.dart");
+
+// Recursively list all Dart files in the current directory.
+void main(List<String> arguments) {
+  for (var entity in dartFile.listSync()) {
+    print(entity.path);
+  }
+}
+```
+
+## Syntax
+
+The glob syntax hews closely to the widely-known Bash glob syntax, with a few
+exceptions that are outlined below.
+
+In order to be as cross-platform and as close to the Bash syntax as possible,
+all globs use POSIX path syntax, including using `/` as a directory separator
+regardless of which platform they're on. This is true even for Windows roots;
+for example, a glob matching all files in the C drive would be `C:/*`.
+
+### Match any characters in a filename: `*`
+
+The `*` character matches zero or more of any character other than `/`. This
+means that it can be used to match all files in a given directory that match a
+pattern without also matching files in a subdirectory. For example, `lib/*.dart`
+will match `lib/glob.dart` but not `lib/src/utils.dart`.
+
+### Match any characters across directories: `**`
+
+`**` is like `*`, but matches `/` as well. It's useful for matching files or
+listing directories recursively. For example, `lib/**.dart` will match both
+`lib/glob.dart` and `lib/src/utils.dart`.
+
+If `**` appears at the beginning of a glob, it won't match absolute paths or
+paths beginning with `../`. For example, `**.dart` won't match `/foo.dart`,
+although `/**.dart` will. This is to ensure that listing a bunch of paths and
+checking whether they match a glob produces the same results as listing that
+glob. In the previous example, `/foo.dart` wouldn't be listed for `**.dart`, so
+it shouldn't be matched by it either.
+
+This is an extension to Bash glob syntax that's widely supported by other glob
+implementations.
+
+### Match any single character: `?`
+
+The `?` character matches a single character other than `/`. Unlike `*`, it
+won't match any more or fewer than one character. For example, `test?.dart` will
+match `test1.dart` but not `test10.dart` or `test.dart`.
+
+### Match a range of characters: `[...]`
+
+The `[...]` construction matches one of several characters. It can contain
+individual characters, such as `[abc]`, in which case it will match any of those
+characters; it can contain ranges, such as `[a-zA-Z]`, in which case it will
+match any characters that fall within the range; or it can contain a mix of
+both. It will only ever match a single character. For example,
+`test[a-zA-Z_].dart` will match `testx.dart`, `testA.dart`, and `test_.dart`,
+but not `test-.dart`.
+
+If it starts with `^` or `!`, the construction will instead match all characters
+*not* mentioned. For example, `test[^a-z].dart` will match `test1.dart` but not
+`testa.dart`.
+
+This construction never matches `/`.
+
+### Match one of several possibilities: `{...,...}`
+
+The `{...,...}` construction matches one of several options, each of which is a
+glob itself. For example, `lib/{*.dart,src/*}` matches `lib/glob.dart` and
+`lib/src/data.txt`. It can contain any number of options greater than one, and
+can even contain nested options.
+
+This is an extension to Bash glob syntax, although it is supported by other
+layers of Bash and is often used in conjunction with globs.
+
+### Escaping a character: `\`
+
+The `\` character can be used in any context to escape a character that would
+otherwise be semantically meaningful. For example, `\*.dart` matches `*.dart`
+but not `test.dart`.
+
+### Syntax errors
+
+Because they're used as part of the shell, almost all strings are valid Bash
+globs. This implementation is more picky, and performs some validation to ensure
+that globs are meaningful. For instance, unclosed `{` and `[` are disallowed.
+
+### Reserved syntax: `(...)`
+
+Parentheses are reserved in case this package adds support for Bash extended
+globbing in the future. For the time being, using them will throw an error
+unless they're escaped.