[Fix] nvm which: show alias name in infinite loop error message

`${2}` was empty because positional parameters had been consumed by `shift` in the argument parsing loop.
Use `${provided_version}` which holds the resolved alias name.

Bug introduced in 1c00753fd9.

nvm.sh

@@ -4374,7 +4374,7 @@ nvm() {
         nvm_err 'System version of node not found.'
         return 127
       elif [ "${VERSION}" = '∞' ]; then
-        nvm_err "The alias \"${2}\" leads to an infinite loop. Aborting."
+        nvm_err "The alias \"${provided_version}\" leads to an infinite loop. Aborting."
         return 8
       fi
 

test/fast/Running 'nvm which' with circular alias shows alias name

@@ -0,0 +1,24 @@
+#!/bin/sh
+
+set -ex
+
+die () { echo "$@" ; cleanup ; exit 1; }
+
+cleanup() {
+  rm -rf "$(nvm_alias_path)/circular_test"
+}
+
+: nvm.sh
+\. ../../nvm.sh
+
+\. ../common.sh
+
+nvm_make_alias circular_test circular_test
+
+try_err nvm which circular_test
+EXPECTED_OUTPUT='The alias "circular_test" leads to an infinite loop. Aborting.'
+[ "_${CAPTURED_STDERR}" = "_${EXPECTED_OUTPUT}" ] \
+  || die "'nvm which circular_test' did not output >${EXPECTED_OUTPUT}<; got >${CAPTURED_STDERR}<"
+[ "_$CAPTURED_EXIT_CODE" = "_8" ] || die "Expected exit code 8; got ${CAPTURED_EXIT_CODE}"
+
+cleanup