Ubuntu fix: don't use . in place of source

If `rbenv init -` outputs `.` in place of `source` and that gets eval'd
by the desktop manager via `~/.profile`, it chokes and prevents the user
from logging in.

Fixes #457

libexec/rbenv-init

@@ -101,7 +101,12 @@ if [[ ":${PATH}:" != *:"${RBENV_ROOT}/shims":* ]]; then
 fi
 
 completion="${root}/completions/rbenv.${shell}"
-[ -r "$completion" ] && echo ". '$completion'"
+if [ -r "$completion" ]; then
+  case "$shell" in
+  fish ) echo ". '$completion'" ;;
+  *    ) echo "source '$completion'" ;;
+  esac
+fi
 
 if [ -z "$no_rehash" ]; then
   echo 'rbenv rehash 2>/dev/null'

test/init.bats

@@ -21,7 +21,7 @@ load test_helper
   root="$(cd $BATS_TEST_DIRNAME/.. && pwd)"
   SHELL=/bin/bash run rbenv-init -
   assert_success
-  assert_line ". '${root}/libexec/../completions/rbenv.bash'"
+  assert_line "source '${root}/libexec/../completions/rbenv.bash'"
 }
 
 @test "setup shell completions (fish)" {