[New] support external install hook “$NVM_INSTALL_THIRD_PARTY_HOOK”.

Fixes #1207.

nvm.sh

@@ -1567,8 +1567,6 @@ nvm_install_binary() {
   local VERSION
   VERSION="$(nvm_strip_iojs_prefix "${PREFIXED_VERSION}")"
 
-  local VERSION_PATH
-
   if [ -z "$(nvm_get_os)" ]; then
     return 2
   fi
@@ -2358,6 +2356,29 @@ nvm() {
         return $?
       fi
 
+      local NVM_INSTALL_SUCCESS
+      if [ -n "${NVM_INSTALL_THIRD_PARTY_HOOK-}" ]; then
+        nvm_err '** $NVM_INSTALL_THIRD_PARTY_HOOK env var set; dispatching to third-party installation method **'
+        local NVM_METHOD_PREFERENCE
+        NVM_METHOD_PREFERENCE='binary'
+        if [ $nobinary -eq 1 ]; then
+          NVM_METHOD_PREFERENCE='source'
+        fi
+        local VERSION_PATH
+        VERSION_PATH="$(nvm_version_path "${VERSION}")"
+        local EXIT_CODE
+        "${NVM_INSTALL_THIRD_PARTY_HOOK}" "${VERSION}" "${FLAVOR}" std "${NVM_METHOD_PREFERENCE}" "${VERSION_PATH}" || {
+          EXIT_CODE=$?
+          nvm_err '*** Third-party $NVM_INSTALL_THIRD_PARTY_HOOK env var failed to install! ***'
+          return $EXIT_CODE
+        }
+        if ! nvm_is_version_installed "${VERSION}"; then
+          nvm_err '*** Third-party $NVM_INSTALL_THIRD_PARTY_HOOK env var claimed to succeed, but failed to install! ***'
+          return 33
+        fi
+        NVM_INSTALL_SUCCESS=true
+      else
+
         if [ "_$NVM_OS" = "_freebsd" ]; then
           # node.js and io.js do not have a FreeBSD binary
           nobinary=1
@@ -2370,7 +2391,6 @@ nvm() {
           fi
         fi
 
-      local NVM_INSTALL_SUCCESS
         # skip binary install if "nobinary" option specified.
         if [ $nobinary -ne 1 ] && nvm_binary_available "$VERSION"; then
           if nvm_install_binary "${FLAVOR}" std "${VERSION}"; then
@@ -2387,6 +2407,8 @@ nvm() {
           fi
         fi
 
+      fi
+
       if [ "$NVM_INSTALL_SUCCESS" = true ] && nvm use "$VERSION"; then
         nvm_ensure_default_set "$provided_version"
         if [ ! -z "$REINSTALL_PACKAGES_FROM" ] \

test/installation_node/install hook

@@ -0,0 +1,40 @@
+#!/bin/sh
+
+die () { echo $@ ; exit 1; }
+
+. ../../nvm.sh
+
+VERSION='v0.11.0'
+VERSION_PATH="$(nvm_version_path "${VERSION}")"
+
+succeed() {
+  nvm_echo "$@"
+  NVM_INSTALL_THIRD_PARTY_HOOK= nvm install "${VERSION}"
+}
+
+fail() {
+  succeed "$@"
+  return 11
+}
+
+! nvm_is_version_installed "${VERSION}" || nvm uninstall "${VERSION}" || die 'uninstall failed'
+
+OUTPUT="$(NVM_INSTALL_THIRD_PARTY_HOOK=succeed nvm install "${VERSION}")"
+USE_OUTPUT="$(nvm use "${VERSION}")"
+EXPECTED_OUTPUT="${VERSION} node std binary ${VERSION_PATH}
+${USE_OUTPUT}
+${USE_OUTPUT}" # double use output is from the normal install in succeed()
+
+[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<; got >${OUTPUT}<"
+
+! nvm_is_version_installed "${VERSION}" || nvm uninstall "${VERSION}" || die 'uninstall 2 failed'
+
+OUTPUT="$(NVM_INSTALL_THIRD_PARTY_HOOK=fail nvm install "${VERSION}" || echo 'failed')"
+USE_OUTPUT="$(nvm use "${VERSION}")"
+EXPECTED_OUTPUT="${VERSION} node std binary ${VERSION_PATH}
+${USE_OUTPUT}
+failed"
+
+[ "${OUTPUT}" = "${EXPECTED_OUTPUT}" ] || die "expected >${EXPECTED_OUTPUT}<; got >${OUTPUT}<"
+
+