Add support for `nvm ls stable` and `nvm ls unstable`

nvm.sh

@@ -274,6 +274,11 @@ nvm_ls() {
     fi
   else
     if [ "_$PATTERN" != "_system" ]; then
+      if nvm_validate_implicit_alias "$PATTERN" 2> /dev/null ; then
+        nvm_ls "$(nvm_print_implicit_alias local "$PATTERN" 2> /dev/null)"
+        return $?
+      fi
+
       local NUM_VERSION_GROUPS
       NUM_VERSION_GROUPS="$(nvm_num_version_groups "$PATTERN")"
       if [ "_$NUM_VERSION_GROUPS" = "_2" ] || [ "_$NUM_VERSION_GROUPS" = "_1" ]; then

test/fast/Listing versions/Running "nvm ls stable" and "nvm ls unstable" should return the appropriate implicit alias

@@ -0,0 +1,25 @@
+ #!/bin/sh
+
+. ../../../nvm.sh
+
+die () { echo $@ ; exit 1; }
+
+EXPECTED_STABLE="$(nvm_print_implicit_alias local stable)"
+STABLE_VERSION="$(nvm_version "$EXPECTED_STABLE")"
+
+EXPECTED_UNSTABLE="$(nvm_print_implicit_alias local unstable)"
+UNSTABLE_VERSION="$(nvm_version "$EXPECTED_UNSTABLE")"
+
+nvm ls stable | \grep "$STABLE_VERSION" >/dev/null \
+  || die "expected 'nvm ls stable' to give $STABLE_VERSION, got $(nvm ls stable)"
+
+nvm ls unstable | \grep "$UNSTABLE_VERSION" >/dev/null \
+  || die "expected 'nvm ls unstable' to give $UNSTABLE_VERSION, got $(nvm ls unstable)"
+
+mkdir ../../../v0.1.2
+nvm alias stable 0.1
+
+nvm ls stable | \grep v0.1.2 >/dev/null \
+  && nvm ls stable | \grep -v "$STABLE_VERSION" >/dev/null \
+  || die "'nvm ls stable' did not contain an explicit 'stable' alias"
+

test/fast/Listing versions/teardown

@@ -11,4 +11,6 @@ rmdir ../../../v0.3.3 >/dev/null 2>&1
 rmdir ../../../v0.3.9 >/dev/null 2>&1
 rmdir ../../../versions >/dev/null 2>&1
 unalias nvm_has_system_node >/dev/null 2>&1
+rm -f ../../../alias/stable >/dev/null 2>&1
+rm -f ../../../alias/unstable >/dev/null 2>&1