Better support of HEAD and listing of zero sized objects with trailing
slash (a.k.a empty directory). For that, isLeafDir function is added
to indicate if the specified object is an empty directory or not. Each
backend (xl, fs) has the responsibility to store that information.
Currently, in both of XL & FS, an empty directory is represented by
an empty directory in the backend.
isLeafDir() checks if the given path is an empty directory or not,
since dir listing is costly if the latter contains too many objects,
readDirN() is added in this PR to list only N number of entries.
In isLeadDir(), we will only list one entry to check if a directory
is empty or not.
Resource strings and paths are case insensitive on windows
deployments but if user happens to use upper case instead of
lower case for certain configuration params like bucket
policies and bucket notification config. We might not honor
them which leads to a wrong behavior on windows.
This is windows only behavior, for all other platforms case
is still kept sensitive.
