Revert "Don't duplicate shims in PATH"

Too many of our users have a shell initialization set up that
inadvertently duplicates some or most of the entries in their PATH,
bringing the system paths again in front of rbenv's shims. If this was a
nested shell (a typical scenario when starting up tmux), `rbenv init`
would get eval'd again but this time, shims won't get added to the front
of the PATH and would only stay and the end of the path, effectively
rendering them useless.

I tried to argue that this is a user problem rather than rbenv's, but I
can't fix everybody shell init when they report bugs. Instead, let's
revert to simpler times in rbenv where we just roll along with the
duplication and don't ask any questions.

This reverts commit 03fa148e81.

Fixes #369

libexec/rbenv-init

@@ -92,22 +92,13 @@ fi
 
 mkdir -p "${RBENV_ROOT}/"{shims,versions}
 
-if [[ ":${PATH}:" != *:"${RBENV_ROOT}/shims":* ]]; then
-  case "$shell" in
-  fish )
-    echo "setenv PATH '${RBENV_ROOT}/shims' \$PATH"
-  ;;
-  * )
-    echo 'export PATH="'${RBENV_ROOT}'/shims:${PATH}"'
-  ;;
-  esac
-fi
-
 case "$shell" in
 fish )
+  echo "setenv PATH '${RBENV_ROOT}/shims' \$PATH"
   echo "setenv RBENV_SHELL $shell"
 ;;
 * )
+  echo 'export PATH="'${RBENV_ROOT}'/shims:${PATH}"'
   echo "export RBENV_SHELL=$shell"
 ;;
 esac

test/init.bats

@@ -64,11 +64,11 @@ load test_helper
   assert_line 0 "setenv PATH '${RBENV_ROOT}/shims' \$PATH"
 }
 
-@test "doesn't add shims to PATH more than once" {
+@test "can add shims to PATH more than once" {
   export PATH="${RBENV_ROOT}/shims:$PATH"
   run rbenv-init - bash
   assert_success
-  refute_line 'export PATH="'${RBENV_ROOT}'/shims:${PATH}"'
+  assert_line 0 'export PATH="'${RBENV_ROOT}'/shims:${PATH}"'
 }
 
 @test "doesn't add shims to PATH more than once (fish)" {