shims: handle symlinked scripts, via new PYENV_FILE_ARG

`PYENV_FILE_ARG` is used here to make use of `abs_dirname` later in
`libexec/pyenv`.

Fixes https://github.com/yyuu/pyenv/issues/404

libexec/pyenv

@@ -54,6 +54,19 @@ else
 fi
 export PYENV_ROOT
 
+# Transfer PYENV_FILE_ARG (from shims) into PYENV_DIR.
+if [ -z "${PYENV_DIR}" ]; then
+  if [ -n "${PYENV_FILE_ARG}" ]; then
+    if [ -L "${PYENV_FILE_ARG}" ]; then
+      PYENV_DIR="$(abs_dirname "${PYENV_FILE_ARG}")"
+    else
+      PYENV_DIR="${PYENV_FILE_ARG%/*}"
+    fi
+    export PYENV_DIR
+    unset PYENV_FILE_ARG
+  fi
+fi
+
 if [ -z "${PYENV_DIR}" ]; then
   PYENV_DIR="$(pwd)"
 else

libexec/pyenv-rehash

@@ -52,7 +52,7 @@ if [[ "\$program" = "python"* ]]; then
     -c* | -- ) break ;;
     */* )
       if [ -f "\$arg" ]; then
-        export PYENV_DIR="\${arg%/*}"
+        export PYENV_FILE_ARG="\$arg"
         break
       fi
       ;;