File identification library for Python.

Given a file (or some information about a file), return a set of standardized tags identifying what the file is.

If you have an actual file on disk, you can get the most information possible (a superset of all other methods):

>>> identify.tags_from_path('/path/to/file.py')
{'file', 'text', 'python', 'non-executable'}
>>> identify.tags_from_path('/path/to/file-with-shebang')
{'file', 'text', 'shell', 'bash', 'executable'}
>>> identify.tags_from_path('/bin/bash')
{'file', 'binary', 'executable'}
>>> identify.tags_from_path('/path/to/directory')
{'directory'}
>>> identify.tags_from_path('/path/to/symlink')
{'symlink'}

When using a file on disk, the checks performed are:

• File type (file, symlink, directory)
• Mode (is it executable?)
• File name (mostly based on extension)
• If executable, the shebang is read and the interpreter interpreted

>>> identify.tags_from_filename('file.py')
{'text', 'python'}

>>> identify.tags_from_interpreter('python3.5')
{'python', 'python3'}
>>> identify.tags_from_interpreter('bash')
{'shell', 'bash'}
>>> identify.tags_from_interpreter('some-unrecognized-thing')
set()

$ identify-cli --help
usage: identify-cli [-h] [--filename-only] path

positional arguments:
  path

optional arguments:
  -h, --help       show this help message and exit
  --filename-only

$ identify-cli setup.py; echo $?
["file", "non-executable", "python", "text"]
0
identify setup.py --filename-only; echo $?
["python", "text"]
0
$ identify-cli wat.wat; echo $?
wat.wat does not exist.
1
$ identify-cli wat.wat --filename-only; echo $?
1

A call to tags_from_path does this:

1. What is the type: file, symlink, directory? If it's not file, stop here.
2. Is it executable? Add the appropriate tag.
3. Do we recognize the file extension? If so, add the appropriate tags, stop here. These tags would include binary/text.
4. Peek at the first X bytes of the file. Use these to determine whether it is binary or text, add the appropriate tag.
5. If identified as text above, try to read and interpret the shebang, and add appropriate tags.

By design, this means we don't need to partially read files where we recognize the file extension.