Revert support for user-installed gems (#1443)

test/rehash.bats

@@ -105,22 +105,17 @@ ruby
 OUT
 }
 
-@test "user-install" {
-  create_executable "${HOME}/.gem/ruby/3.0.0/bin/lolcat"
+@test "no shims for user-installed gems" {
+  create_executable "2.7.5" "ruby"
+  create_executable "3.1.2" "ruby"
+  create_executable "${HOME}/.gem/ruby/2.7.0/bin/lolcat"
   create_executable "${HOME}/.gem/ruby/3.1.0/bin/pinecone"
 
-  assert [ ! -e "${RBENV_ROOT}/shims/lolcat" ]
-  assert [ ! -e "${RBENV_ROOT}/shims/pinecone" ]
-
   run rbenv-rehash
   assert_success ""
 
-  run ls "${RBENV_ROOT}/shims"
-  assert_success
-  assert_output <<OUT
-lolcat
-pinecone
-OUT
+  assert [ ! -e "${RBENV_ROOT}/shims/lolcat" ]
+  assert [ ! -e "${RBENV_ROOT}/shims/pinecone" ]
 }
 
 @test "explicit gem home" {

test/which.bats

@@ -98,11 +98,11 @@ The \`rspec' command exists in these Ruby versions:
 OUT
 }
 
-@test "executable found in user gems" {
+@test "executable not found in user gems" {
   create_executable "2.7.6" "ruby"
   create_executable "${HOME}/.gem/ruby/2.7.0/bin" "rake"
   GEM_HOME='' RBENV_VERSION=2.7.6 run rbenv-which rake
-  assert_success "${HOME}/.gem/ruby/2.7.0/bin/rake"
+  assert_failure
 }
 
 @test "executable found in gem home" {
@@ -113,6 +113,13 @@ OUT
   assert_success "${HOME}/mygems/bin/rake"
 }
 
+@test "executable found in gem home (system ruby)" {
+  create_executable "${HOME}/mygems/bin" "rbenv-test-lolcat"
+  create_executable "${HOME}/.gem/ruby/2.6.0/bin" "rbenv-test-lolcat"
+  GEM_HOME="${HOME}/mygems" RBENV_VERSION=system run rbenv-which rbenv-test-lolcat
+  assert_success "${HOME}/mygems/bin/rbenv-test-lolcat"
+}
+
 @test "carries original IFS within hooks" {
   create_hook which hello.bash <<SH
 hellos=(\$(printf "hello\\tugly world\\nagain"))