101 

   102 @templatefilter('commonprefix')

   103 def commonprefix(filelist):

   104     """List of text. Treats each list item as file name with /

   105     as path separator and returns the longest common directory

   106     prefix shared by all list items.

   107     Returns the empty string if no common prefix exists.

   108 

   109     The list items are not normalized, i.e. "foo/../bar" is handled as

   110     file "bar" in the directory "foo/..". Leading slashes are ignored.

   111 

   112     For example, ["foo/bar/baz", "foo/baz/bar"] becomes "foo" and

   113     ["foo/bar", "baz"] becomes "".

   114     """

   115     def common(a, b):

   116         if len(a) > len(b):

   117             a = b[:len(a)]

   118         elif len(b) > len(a):

   119             b = b[:len(a)]

   120         if a == b:

   121             return a

   122         for i in xrange(len(a)):

   123             if a[i] != b[i]:

   124                 return a[:i]

   125         return a

   126     try:

   127         if not filelist:

   128             return ""

   129         dirlist = [f.lstrip('/').split('/')[:-1] for f in filelist]

   130         if len(dirlist) == 1:

   131             return '/'.join(dirlist[0])

   132         a = min(dirlist)

   133         b = max(dirlist)

   134         # The common prefix of a and b is shared with all

   135         # elements of the list since Python sorts lexicographical

   136         # and [1, x] after [1].

   137         return '/'.join(common(a, b))

   138     except TypeError:

   139         raise error.ParseError(_('argument is not a list of text'))