|If true, uses the /a/ab/foo.jpg directory structure.
|其他设置： 按首字母排序 | 按功能排序|
true, uploaded files will be distributed into sub-directories of $wgUploadDirectory based on the first two characters of the md5 hash of the filename.
Creation of such subdirectories is handled automatically.
This is used to avoid having too many files in one folder because some filesystems don't perform well with large numbers of files in one folder.
The algorithm for that is based on a md5 of the name, the first hex character is used for the first directory, then the first two characters are used for the subdirectory.
Foo.png→ md5 of filename =
f865cbca12286c1c5b7616b4a70fbf68→ f + f8 = $IP/images/f/f8/Foo.png
If you set $wgLocalFileRepo, this variable will be ignored.