update doc

docs/howto/howto.md

@@ -43,3 +43,7 @@
 ## Symlink dotfiles
 
 [Symlink dotfiles](symlink-dotfiles.md)
+
+## Prompt user for variables
+
+[Prompt user for variables](prompt-user-for-variables.md)

docs/howto/prompt-user-for-variables.md

@@ -0,0 +1,26 @@
+# Prompt user for variables
+
+With the use of [uservariables](config-details.md#entry-uservariables),
+one can define specific variables that need to be initially filled in manually
+by the user on first run.
+
+The provided values are then automatically saved by dotdrop to `uservariables.yaml`,
+which can be included in the main config as a file from which variables are imported
+using [import_variables](config-details.md#entry-import_variables).
+
+Let's say for example that you want to provide manually the email value
+on new hosts you deploy your dotfiles to.
+
+You'd add the following elements to your config:
+```yaml
+uservariables:
+  emailvar: "email"
+config:
+  import_variables:
+    - uservariables.yaml:optional
+```
+
+On first run, the `emailvar` is prompted to the user and then saved
+to `uservariables.yaml`. Since this file is imported, the value for
+`emailvar` will automatically be filled in without prompting the
+user on subsequent calls.