How to reset anaconda root environment
Solution 1:
See https://github.com/conda/conda/issues/1032
This has been implemented as
conda list --revisionsandconda install --rev REV_NUM.
EDIT: be careful though if you execute conda install --rev 0 as this will remove your root environment and the conda command. Maybe conda install --rev 1 would produce the desired behavior (restore root environment to its state after first installation).
EDIT 2018-03-07: Use the --revision argument instead of --rev