Previously, the shims directory was only excluded for system versions,
which meant that `asdf exec` would fall back to a shim if the install
didn't have the desired binary. If the shims are up to date this isn't a
problem since we check the metadata, but it causes issues if those are
out of sync for whatever reason.
I've checked all the uses of this function and I'm not seeing anywhere
we should need the old behavior.
- Make shim-exec, shim-env, and which use the same logic to look for commands
- Make sure shim-exec and which use a plugin exec-path hook as documented
(the hook takes a relative path to the executable and returns also
a relative path, possibly modified)
- Fix shellchecks
Previously, if we ran a command like `asdf install` and we encountered a
plugin that didn't exist, asdf produces an error saying "No such
plugin". Without knowing which plugin it could be referring too, we'd
have to manually go through each plugin in `.tool-versions` to find the
culprit.
With this commit, we'll now also include the plugin name as part of the
messaging for easier debugging.
