Add nvm_tree_contains_path function

nvm.sh

@@ -53,6 +53,19 @@ if [ -z "$NVM_NODEJS_ORG_MIRROR" ]; then
   export NVM_NODEJS_ORG_MIRROR="http://nodejs.org/dist"
 fi
 
+nvm_tree_contains_path() {
+  local tree
+  tree="$1"
+  local path
+  path="$2"
+  local pathdir
+  pathdir=$(dirname "$path")
+  while [ "$pathdir" != "" ] && [ "$pathdir" != "." ] && [ "$pathdir" != "/" ] && [ "$pathdir" != "$tree" ]; do
+    pathdir=$(dirname "$pathdir")
+  done
+  [ "$pathdir" = "$tree" ]
+}
+
 # Traverse up in directory tree to find containing folder
 nvm_find_up() {
   local path

test/fast/Unit tests/nvm_tree_contains_path

@@ -0,0 +1,27 @@
+#!/bin/sh
+
+cleanup () {
+  rm tmp/node
+  rmdir tmp
+  rm tmp2/node
+  rmdir tmp2
+}
+die () { echo $@ ; cleanup; exit 1; }
+
+. ../../../nvm.sh
+
+mkdir -p tmp
+touch -p tmp/node
+mkdir -p tmp2
+touch -p tmp2/node
+
+nvm_tree_contains_path tmp tmp/node || die '"tmp" should contain "tmp/node"'
+
+nvm_tree_contains_path tmp tmp2/node && die '"tmp" should not contain "tmp2/node"'
+
+nvm_tree_contains_path tmp2 tmp2/node || die '"tmp2" should contain "tmp2/node"'
+
+nvm_tree_contains_path tmp2 tmp/node && die '"tmp2" should not contain "tmp/node"'
+
+cleanup
+