dirname function
Gets the part of path before the last separator.
p.dirname('path/to/foo.dart'); // -> 'path/to'
p.dirname('path/to');          // -> 'path'
Trailing separators are ignored.
p.dirname('path/to/'); // -> 'path'
If an absolute path contains no directories, only a root, then the root is returned.
p.dirname('/');  // -> '/' (posix)
p.dirname('c:\');  // -> 'c:\' (windows)
If a relative path has no directories, then '.' is returned.
p.dirname('foo');  // -> '.'
p.dirname('');  // -> '.'
Implementation
String dirname(String path) => context.dirname(path);