Created attachment 843492 [details]
Anaconda screenshot (KVM reproducer).

Description of problem:
I have huge RAID5 over all my disks as /.  With former Anaconda when yum distro upgrade broke my system I did
  cd /; mkdir old;mv * old/
and installed new OS there without reformatting the partition.
New Anaconda insists on clicking "reformat".  Where should I move out 1.5TB of my data?
I have off-site backup of important parts of it but that is off-topic here.

Version-Release number of selected component (if applicable):
Fedora-20-x86_64-DVD.iso GA

How reproducible:
Always.

Steps to Reproduce:
1. Install any Fedora (used LUKS on top of mdadm RAID5) with one partition /.
   (Used also non-LUKS mdadm RAID1 /boot and LUKS mdadm RAID5 swap.)
2. cd /; mkdir old;mv * old/
3. Try to install new Fedora 20 x86_64 on top of it, preserving old/ there.

Actual results:
After clicking
  Mount Point: /
  Not checked "reformat".
  Update settings
Mount Point entry is cleared and the partition is not added to "New Fedora 20 Installation".

The screenshot shows a case where I put "Mount Point: /foo" there first clicking "reformat" and later cleared the checkbox "reformat".
Second screenshot shows that Anaconda still does not allow me to install Fedora.

Expected results:
Normally installed Fedora along the preserved "/old" directory.
I was using it regularly till approx. Fedora 15 or which version switched to new Anaconda.

Additional info:
Please no advices for more partitions (system+data).  That has no technical justification (besides workarounding an Anaconda regression).