The literal tilde in a PATH entry (e.g. `~/.rbenv/shims`) doesn't seem
to be supported by system `which` utility, but *does* seem to be
supported by `command -v` (used in `rbenv-which`) and `type -p`.
Therefore, we must strip away `~/.rbenv/shims` from PATH when looking up
executables for system Ruby, lest we risk infinite loop. We do so by
substituting any occurence of `~` in PATH with the value of `HOME`.
If `foo` didn't exist and `RBENV_VERSION=system rbenv which foo` was
called, the error message used to be misleading:
rbenv: version `system' is not installed
Instead, have the error message simply say that the command was not found.
Fixes#770
Delegate to `rbenv-shims` instead of `rbenv shims` and therefore skip
going through the main `rbenv` executable again that would set up a lot
of the environment that was already set.
Running any shim (and thus `rbenv-exec`) would always execute
`rbenv-version-name` twice: once in `rbenv-exec` and another time in
`rbenv-which`, even though RBENV_VERSION variable would have already
been populated at this point.
Now RBENV_VERSION is respected within `rbenv-which`.
Docs are comprised from "Usage", "Summary" and "Help" sections, where
"Help" can span multiple commented lines. If it is missing, "Summary" is
shown in its place.
References #204, references #206