Implement multitree lunch

Test: (cd build/make/orchestrator/core ; ./test_lunch.py)
Change-Id: I4ba36a79abd13c42b986e3ba0d6d599c1cc73cb0

envsetup.sh

@@ -425,6 +425,61 @@ function addcompletions()
     complete -F _complete_android_module_names m
 }
 
+function multitree_lunch_help()
+{
+    echo "usage: lunch PRODUCT-VARIANT" 1>&2
+    echo "    Set up android build environment based on a product short name and variant" 1>&2
+    echo 1>&2
+    echo "lunch COMBO_FILE VARIANT" 1>&2
+    echo "    Set up android build environment based on a specific lunch combo file" 1>&2
+    echo "    and variant." 1>&2
+    echo 1>&2
+    echo "lunch --print [CONFIG]" 1>&2
+    echo "    Print the contents of a configuration.  If CONFIG is supplied, that config" 1>&2
+    echo "    will be flattened and printed.  If CONFIG is not supplied, the currently" 1>&2
+    echo "    selected config will be printed.  Returns 0 on success or nonzero on error." 1>&2
+    echo 1>&2
+    echo "lunch --list" 1>&2
+    echo "    List all possible combo files available in the current tree" 1>&2
+    echo 1>&2
+    echo "lunch --help" 1>&2
+    echo "lunch -h" 1>&2
+    echo "    Prints this message." 1>&2
+}
+
+function multitree_lunch()
+{
+    local code
+    local results
+    if $(echo "$1" | grep -q '^-') ; then
+        # Calls starting with a -- argument are passed directly and the function
+        # returns with the lunch.py exit code.
+        build/make/orchestrator/core/lunch.py "$@"
+        code=$?
+        if [[ $code -eq 2 ]] ; then
+          echo 1>&2
+          multitree_lunch_help
+          return $code
+        elif [[ $code -ne 0 ]] ; then
+          return $code
+        fi
+    else
+        # All other calls go through the --lunch variant of lunch.py
+        results=($(build/make/orchestrator/core/lunch.py --lunch "$@"))
+        code=$?
+        if [[ $code -eq 2 ]] ; then
+          echo 1>&2
+          multitree_lunch_help
+          return $code
+        elif [[ $code -ne 0 ]] ; then
+          return $code
+        fi
+
+        export TARGET_BUILD_COMBO=${results[0]}
+        export TARGET_BUILD_VARIANT=${results[1]}
+    fi
+}
+
 function choosetype()
 {
     echo "Build type choices are:"