[Fix] nvm: do not change or export the caller's IFS

`IFS=... nvm "$@"` is a prefix assignment to a function call, which bash's POSIX mode (macOS `/bin/sh`) keeps after the call returns, and exports.

nvm.sh

@@ -3672,14 +3672,18 @@ nvm() {
   if [ "${-#*e}" != "$-" ]; then
     set +e
     local EXIT_CODE
-    IFS="${DEFAULT_IFS}" nvm "$@"
+    local IFS
+    IFS="${DEFAULT_IFS}"
+    nvm "$@"
     EXIT_CODE="$?"
     set -e
     return "$EXIT_CODE"
   elif [ "${-#*a}" != "$-" ]; then
     set +a
     local EXIT_CODE
-    IFS="${DEFAULT_IFS}" nvm "$@"
+    local IFS
+    IFS="${DEFAULT_IFS}"
+    nvm "$@"
     EXIT_CODE="$?"
     set -a
     return "$EXIT_CODE"
@@ -3687,13 +3691,17 @@ nvm() {
     # shellcheck disable=SC3041
     set +E
     local EXIT_CODE
-    IFS="${DEFAULT_IFS}" nvm "$@"
+    local IFS
+    IFS="${DEFAULT_IFS}"
+    nvm "$@"
     EXIT_CODE="$?"
     # shellcheck disable=SC3041
     set -E
     return "$EXIT_CODE"
   elif [ "${IFS}" != "${DEFAULT_IFS}" ]; then
-    IFS="${DEFAULT_IFS}" nvm "$@"
+    local IFS
+    IFS="${DEFAULT_IFS}"
+    nvm "$@"
     return "$?"
   fi
 

test/fast/Running 'nvm' should not change or export the caller's IFS

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+die () { IFS=' '; echo "$@" ; exit 1; }
+
+: nvm.sh
+\. ../../nvm.sh
+
+IFS=':'
+nvm --version >/dev/null
+[ "${IFS}" = ':' ] || die "nvm changed the caller's IFS; got >${IFS}<"
+
+set -e
+nvm --version >/dev/null
+set +e
+[ "${IFS}" = ':' ] || die "nvm changed the caller's IFS under set -e; got >${IFS}<"
+
+! env | grep -q '^IFS=' || die 'nvm exported IFS'
+
+IFS=' '