`is-nan@1.0.0` was published on 2014-07-05 and unpublished minutes later
(the registry's `time` map still lists it, but `versions` jumps from `0.0.0` to `1.0.1`),
so `npm install -g is-nan@1.0.0` fails with `ETARGET`,
and the regression test added in ce157343 fails deterministically in every shell.
See https://github.com/nvm-sh/nvm/actions/runs/28407118533
When `nvm install <target>` found that `<target>` was already installed,
the post-`nvm use` steps
(`--reinstall-packages-from`, default packages, and `--alias`/`--default`)
were gated on `[ $EXIT_CODE -ne 0 ]`.
Since that branch is only entered when `nvm use` succeeded (EXIT_CODE == 0),
those conditions were always false, so the steps were silently skipped.
The fresh-install branch correctly uses `-eq 0`;
mirror that here so `--reinstall-packages-from` actually migrates global packages
(and the alias/default get set) when the target version already exists.
Includes a regression test covering the already-installed path.
Fixes#3858
Jordan Harband
Peter Dave HelloandJordan Harband
Qiangjun RanandJordan Harband