Introduce kickstart.user.exec

docs/kickstart/user/exec.md

@@ -0,0 +1,18 @@
+# kickstart.user.exec user command
+
+Execute `command` as `user`.
+It makes kickstart functions available to be used.
+To use variables, like `~`, quote it, otherwise it will be resolved by the current user.
+
+### Example
+
+```bash
+$ kickstart.user.exec vagrant whoami
+vagrant
+
+$ kickstart.user.exec vagrant kickstart.os
+Ubuntu
+
+$ kickstart.user.exec vagrant 'cd ~; pwd'
+/home/vagrant
+```