[Fix] install-latest-npm: npm v6.10 breaks on node v6.0, v6.1, and v9.0-v9.2

Author: ljharb

nvm.sh

@@ -223,13 +223,29 @@ nvm_install_latest_npm() {
 
     local NVM_IS_6_OR_ABOVE
     NVM_IS_6_OR_ABOVE=0
+    local NVM_IS_6_2_OR_ABOVE
+    NVM_IS_6_2_OR_ABOVE=0
     if [ $NVM_IS_5_OR_ABOVE -eq 1 ] && nvm_version_greater_than_or_equal_to "${NODE_VERSION}" 6.0.0; then
       NVM_IS_6_OR_ABOVE=1
+      if nvm_version_greater_than_or_equal_to "${NODE_VERSION}" 6.2.0; then
+        NVM_IS_6_2_OR_ABOVE=1
+      fi
+    fi
+
+    local NVM_IS_9_OR_ABOVE
+    NVM_IS_9_OR_ABOVE=0
+    local NVM_IS_9_3_OR_ABOVE
+    NVM_IS_9_3_OR_ABOVE=0
+    if [ $NVM_IS_6_2_OR_ABOVE -eq 1 ] && nvm_version_greater_than_or_equal_to "${NODE_VERSION}" 9.0.0; then
+      NVM_IS_9_OR_ABOVE=1
+      if nvm_version_greater_than_or_equal_to "${NODE_VERSION}" 9.3.0; then
+        NVM_IS_9_3_OR_ABOVE=1
+      fi
     fi
 
-    if [ $NVM_IS_4_4_OR_BELOW -eq 1 ] || (\
-      [ $NVM_IS_5_OR_ABOVE -eq 1 ] && nvm_version_greater 5.10.0 "${NODE_VERSION}" \
-    ); then
+    if [ $NVM_IS_4_4_OR_BELOW -eq 1 ] || {
+      [ $NVM_IS_5_OR_ABOVE -eq 1 ] && nvm_version_greater 5.10.0 "${NODE_VERSION}"; \
+    }; then
       nvm_echo '* `npm` `v5.3.x` is the last version that works on `node` 4.x versions below v4.4, or 5.x versions below v5.10, due to `Buffer.alloc`'
       $NVM_NPM_CMD install -g npm@5.3
     elif [ $NVM_IS_4_4_OR_BELOW -eq 0 ] && nvm_version_greater 4.7.0 "${NODE_VERSION}"; then
@@ -238,6 +254,12 @@ nvm_install_latest_npm() {
     elif [ $NVM_IS_6_OR_ABOVE -eq 0 ]; then
       nvm_echo '* `npm` `v5.x` is the last version that works on `node` below `v6.0.0`'
       $NVM_NPM_CMD install -g npm@5
+    elif \
+      { [ $NVM_IS_6_OR_ABOVE -eq 1 ] && [ $NVM_IS_6_2_OR_ABOVE -eq 0 ]; } \
+      || { [ $NVM_IS_9_OR_ABOVE -eq 1 ] && [ $NVM_IS_9_3_OR_ABOVE -eq 0 ]; } \
+    ; then
+      nvm_echo '* `npm` `v6.9` is the last version that works on `node` `v6.0.x`, `v6.1.x`, `v9.0.x`, `v9.1.x`, or `v9.2.x`'
+      $NVM_NPM_CMD install -g npm@6.9
     else
       nvm_echo '* Installing latest `npm`; if this does not work on your node version, please report a bug!'
       $NVM_NPM_CMD install -g npm