- Ran `arc set-config history.immutable true` to set the flag in my user settings.
- Ran `arc get-config` to verify that the setting overrode system/user settings:
```
epriestley@orbital ~/dev/phabricator $ arc get-config history.immutable --verbose
history.immutable
If true, arc will never change repository history (e.g., through amending
or rebasing). Defaults to true in Mercurial and false in Git. This
setting has no effect in Subversion.
Example Value: false
Current Value: false
Current Source: project
local Value: -
project Value: false
user Value: true
system Value: -
default Value: -
```