Remove support for legacy global version files

`default` was made legacy back in 2011 with
5be66da (the command was renamed from
`rbenv-default` to `rbenv-global`, and so the global file was renamed
from `$RBENV_ROOT/default` to `$RBENV_ROOT/global` (the latter taking
precedence)

`global` was then made legacy about a month later in Sep 2011 when the
preferred filename was changed to `$RBENV_ROOT/version`.

libexec/rbenv-global

@@ -27,8 +27,5 @@ RBENV_VERSION_FILE="${RBENV_ROOT}/version"
 if [ -n "$RBENV_VERSION" ]; then
   rbenv-version-file-write "$RBENV_VERSION_FILE" "$RBENV_VERSION"
 else
-  rbenv-version-file-read "$RBENV_VERSION_FILE" ||
-  rbenv-version-file-read "${RBENV_ROOT}/global" ||
-  rbenv-version-file-read "${RBENV_ROOT}/default" ||
-  echo system
+  rbenv-version-file-read "$RBENV_VERSION_FILE" || echo system
 fi

libexec/rbenv-version-file

@@ -25,15 +25,7 @@ find_local_version_file() {
 find_global_version_file() {
   local global_version_file="${RBENV_ROOT}/version"
 
-  if [ -e "$global_version_file" ]; then
-    echo "$global_version_file"
-  elif [ -e "${RBENV_ROOT}/global" ]; then
-    echo "${RBENV_ROOT}/global"
-  elif [ -e "${RBENV_ROOT}/default" ]; then
-    echo "${RBENV_ROOT}/default"
-  else
-    echo "$global_version_file"
-  fi
+  echo "$global_version_file"
 }
 
 if [ -n "$target_dir" ]; then

test/global.bats

@@ -3,7 +3,7 @@
 load test_helper
 
 @test "default" {
-  run rbenv global
+  run rbenv-global
   assert_success
   assert_output "system"
 }
@@ -20,7 +20,7 @@ load test_helper
   mkdir -p "$RBENV_ROOT/versions/1.2.3"
   run rbenv-global "1.2.3"
   assert_success
-  run rbenv global
+  run rbenv-global
   assert_success "1.2.3"
 }
 

test/version-file.bats

@@ -12,29 +12,15 @@ create_file() {
   touch "$1"
 }
 
-@test "prints global file if no version files exist" {
-  assert [ ! -e "${RBENV_ROOT}/version" ]
-  assert [ ! -e ".ruby-version" ]
+@test "detects global 'version' file" {
+  create_file "${RBENV_ROOT}/version"
   run rbenv-version-file
   assert_success "${RBENV_ROOT}/version"
 }
 
-@test "detects 'global' file" {
-  create_file "${RBENV_ROOT}/global"
-  run rbenv-version-file
-  assert_success "${RBENV_ROOT}/global"
-}
-
-@test "detects 'default' file" {
-  create_file "${RBENV_ROOT}/default"
-  run rbenv-version-file
-  assert_success "${RBENV_ROOT}/default"
-}
-
-@test "'version' has precedence over 'global' and 'default'" {
-  create_file "${RBENV_ROOT}/version"
-  create_file "${RBENV_ROOT}/global"
-  create_file "${RBENV_ROOT}/default"
+@test "prints global file if no version files exist" {
+  assert [ ! -e "${RBENV_ROOT}/version" ]
+  assert [ ! -e ".ruby-version" ]
   run rbenv-version-file
   assert_success "${RBENV_ROOT}/version"
 }