This commit removes DeprecatedString's "null" state, and replaces all
its users with one of the following:
- A normal, empty DeprecatedString
- Optional<DeprecatedString>
Note that null states of DeprecatedFlyString/StringView/etc are *not*
affected by this commit. However, DeprecatedString::empty() is now
considered equal to a null StringView.
This option, often used with only a lonely dash, allows to "simulate a
login". For now, it just changes the current directory to the home of
the new user.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
Now that we've moved to atomic replacement of these files when altering
them, we don't need to keep them open for the lifetime of Core::Account
so just simplify this and close them when they are not needed.
