Make adding $PYENV_ROOT/bin to PATH independent of other software (#2837)

Fixes breakage in WSL with Pyenv-win installed in the host system;
doesn't affect other supported installation scenarios.

README.md

@@ -317,14 +317,14 @@ See [Advanced configuration](#advanced-configuration) for details and more confi
     * to add to `~/.bash_profile`:
       ~~~ bash
       echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bash_profile
-      echo 'command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bash_profile
+      echo '[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bash_profile
       echo 'eval "$(pyenv init -)"' >> ~/.bash_profile
       ~~~
 
   - For **Zsh**:
     ~~~ zsh
     echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.zshrc
-    echo 'command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.zshrc
+    echo '[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.zshrc
     echo 'eval "$(pyenv init -)"' >> ~/.zshrc
     ~~~
 

libexec/pyenv-init

@@ -165,7 +165,7 @@ function help_() {
       fi
       echo
       echo 'export PYENV_ROOT="$HOME/.pyenv"'
-      echo 'command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"'
+      echo '[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"'
       echo 'eval "$(pyenv init -)"'
       ;;
     esac