Add -d, --dir option to install to <prefix>/<definition> instead of <…

…prefix>

* Similar to ruby-install's -r, --rubies-dir flag.

bin/ruby-build

@@ -8,6 +8,7 @@
 #   --definitions   List all local definitions, including outdated ones
 #   --version       Show version of ruby-build
 #
+#   -d, --dir       Install the Ruby in <prefix>/<definition> instead of <prefix>
 #   -v, --verbose   Verbose mode: forward all build output to stdout/stderr
 #   -p, --patch     Apply a patch from stdin before building
 #   -k, --keep      Do not remove source tree after installation
@@ -1358,6 +1359,7 @@ unset HAS_PATCH
 unset IPV4
 unset IPV6
 unset EARLY_EXIT
+unset APPEND_DEFINITION_TO_PREFIX
 
 RUBY_BUILD_INSTALL_PREFIX="$(abs_dirname "$0")/.."
 
@@ -1378,6 +1380,9 @@ for option in "${OPTIONS[@]}"; do
   "l" | "list")
     EARLY_EXIT=list_maintained_versions
     ;;
+  "d" | "dir")
+    APPEND_DEFINITION_TO_PREFIX=true
+    ;;
   "k" | "keep" )
     KEEP_BUILD_PATH=true
     ;;
@@ -1425,6 +1430,10 @@ if [ "${#EXTRA_ARGUMENTS[@]}" -gt 0 ]; then
   RUBY_CONFIGURE_OPTS_ARRAY=("${EXTRA_ARGUMENTS[@]}")
 fi
 
+if [ "$APPEND_DEFINITION_TO_PREFIX" = "true" ]; then
+  PREFIX_PATH="$PREFIX_PATH/$(basename "$DEFINITION_PATH")"
+fi
+
 case "$EARLY_EXIT" in
 help )
   version