Track progress of entities parsing

Parsing big entities.xml files may take hours. Currently, no progress is shown in the UI, which might give the feeling that the "analysing the confluence package" step in the confluence migrator pro app is stuck.

A progress would help.

Workaround from the server: track the read position of the entities.xml file in the XWiki procfs directory like this:

First, find which process under which file descriptor that is accessing your entities.xml file with lsof:
sudo lsof /path/to/entities.xmlCOMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAMEjava 18271 raph 903r REG 0,44 5547016484 31274428 /path/to/entities.xml
Now that you have the PID (here, 18271) and the file descriptor (FD) (903, read only), on Linux you can ask the kernel what's going on using the proc filesystem:
cat /proc/18271/fdinfo/903 pos: 682276872flags: 0100000mnt_id: 55ino: 31274428
Divide the pos field with the SIZE field of the previous command and you have the progress. I get 0,1229988902985924, which means 12% of progress.