Compare the files named f1 and f2, returning 1 if
they seem equal, 0 otherwise.
Unless shallow is given and is false, files with identical
os.stat() signatures are taken to be equal. If
use_statcache is given and is true,
statcache.stat() will be called rather then
os.stat(); the default is to use os.stat().
Files that were compared using this function will not be compared again
unless their os.stat() signature changes. Note that using
use_statcache true will cause the cache invalidation mechanism to
fail -- the stale stat value will be used from statcache's
cache.
Note that no external programs are called from this function, giving it
portability and efficiency.
Returns three lists of file names: match, mismatch,
errors. match contains the list of files match in both
directories, mismatch includes the names of those that don't,
and errros lists the names of files which could not be
compared. Files may be listed in errors because the user may
lack permission to read them or many other reasons, but always that
the comparison could not be done for some reason.
The shallow and use_statcache parameters have the same
meanings and default values as for filecmp.cmp().