Strip in the best way the extension from a filename.

    >>> file_strip_ext("foo.tar.gz")
    'foo'
    >>> file_strip_ext("foo.buz.gz")
    'foo.buz'
    >>> file_strip_ext("foo.buz")
    'foo'
    >>> file_strip_ext("foo.buz", only_known_extensions=True)
    'foo.buz'
    >>> file_strip_ext("foo.buz;1", skip_version=False,
    ... only_known_extensions=True)
    'foo.buz;1'
    >>> file_strip_ext("foo.gif;icon")
    'foo'
    >>> file_strip_ext("foo.gif;icon", only_know_extensions=True,
    ... allow_subformat=False)
    'foo.gif;icon'

    @param afile: the path/name of a file.
    @type afile: string
    @param skip_version: whether to skip a trailing ";version".
    @type skip_version: bool
    @param only_known_extensions: whether to strip out only known extensions or
        to consider as extension anything that follows a dot.
    @type only_known_extensions: bool
    @param allow_subformat: whether to consider also subformats as part of
        the extension.
    @type allow_subformat: bool
    @return: the name/path without the extension (and version).
    @rtype: string

def file_strip_ext(
        afile,
        skip_version=False,
        only_known_extensions=False,
        allow_subformat=True):
    """
    Strip in the best way the extension from a filename.

    >>> file_strip_ext("foo.tar.gz")
    'foo'
    >>> file_strip_ext("foo.buz.gz")
    'foo.buz'
    >>> file_strip_ext("foo.buz")
    'foo'
    >>> file_strip_ext("foo.buz", only_known_extensions=True)
    'foo.buz'
    >>> file_strip_ext("foo.buz;1", skip_version=False,
    ... only_known_extensions=True)
    'foo.buz;1'
    >>> file_strip_ext("foo.gif;icon")
    'foo'
    >>> file_strip_ext("foo.gif;icon", only_know_extensions=True,
    ... allow_subformat=False)
    'foo.gif;icon'

    @param afile: the path/name of a file.
    @type afile: string
    @param skip_version: whether to skip a trailing ";version".
    @type skip_version: bool
    @param only_known_extensions: whether to strip out only known extensions or
        to consider as extension anything that follows a dot.
    @type only_known_extensions: bool
    @param allow_subformat: whether to consider also subformats as part of
        the extension.
    @type allow_subformat: bool
    @return: the name/path without the extension (and version).
    @rtype: string
    """
    import os
    afile = afile.split(';')
    if len(afile) > 1 and allow_subformat and not afile[-1].isdigit():
        afile = afile[0:-1]
    if len(afile) > 1 and skip_version and afile[-1].isdigit():
        afile = afile[0:-1]
    afile = ';'.join(afile)
    nextfile = _extensions.sub('', afile)
    if nextfile == afile and not only_known_extensions:
        nextfile = os.path.splitext(afile)[0]
    while nextfile != afile:
        afile = nextfile
        nextfile = _extensions.sub('', afile)
    return nextfile