`nvm_install_binary` set the alias from its caller's variables,
so a source install or an `$NVM_INSTALL_THIRD_PARTY_HOOK` install never got it,
and no fresh install wrote `.nvmrc`.
Apply both at the end of `nvm install`, after the install is validated.
`--lts` without a version, or `lts/*`, leaves no provided version,
and `nvm alias` treats an empty target as `nvm unalias`:
`nvm install --lts --default` on an installed version removed the default alias.
In that case point the alias at `lts/<name>`, as the default alias already is.
Yashvardhan Thanvi
d190476345