Re: [PATCH 3/7] Extract, test and enhance the logic to collapse ../foo paths.

Eric Wong wrote:

It should probably just return the root path ("c:/" and
"http://www.example.com/" respectively).

That means recognizing drive letters and URLs.  Hm.

Subversion commands seem to use svn_client_args_to_target_array2
to canonicalize arguments.  It does something like the following:

 1. split at @PEG revision
 2. check if it looks like a URL (svn_path_is_url).  If so:

    i.   urlencode characters with high bit set (svn_path_uri_from_iri)
    ii.  urlencode some other special characters (svn_path_uri_autoescape)
         (that is: [ "<>\\^`{|}])
    iii. (on Windows) convert backslashes to forward slashes
    iv.  complain if there are any '..' (svn_path_is_backpath_present)
    v.   make url scheme and hostname lowercase, strip default portnumber,
	 strip trailing '/', collapse '/'-es including urlencoded %2F,
	 strip '.' and '%2E' components, make drive letter in file:///
         URLs uppercase, urlencode uri-special characters
         (svn_uri_canonicalize)

   Otherwise:

    i.   canonicalize case, handle '..' and '.' components, and make
	 path separators into '/'
         (apr_filepath_merge(APR_FILEPATH_TRUENAME))
    ii.  strip trailing '/', collapse '/'-es except in UNC paths,
         strip '.' components, make drive letter uppercase
         (svn_dirent_canonicalize)
    iii. deal with "truepath collisions" (unwanted case
         canonicalizations)
    iv.  reject .svn and _svn directories

Maybe we can use apr_filepath_merge() to avoid reinventing the wheel?