Document --backup import behaviour

content/docs/command-reference/import.md

@@ -10,7 +10,7 @@ the import.
 ## Synopsis
 
 ```usage
-usage: dvc import [-h] [-q | -v] [-o <path>] [--rev <commit>] url path
+usage: dvc import [-h] [-q | -v] [-o <path>] [--rev <commit>] [--backup] url path
 
 positional arguments:
   url              Location of DVC or Git repository to download from
@@ -91,13 +91,32 @@ from the source repo.
   > [Importing and updating fixed revisions](#example-importing-and-updating-fixed-revisions)
   > example below).
 
+- `-b`, `--backup` - imports files in "backup mode": see Backup Mode section for
+  details.
+
 - `-h`, `--help` - prints the usage/help message, and exit.
 
 - `-q`, `--quiet` - do not write anything to standard output. Exit with 0 if no
   problems arise, otherwise 1.
 
 - `-v`, `--verbose` - displays detailed tracing information.
 
+## Backup Mode
+
+To avoid duplicating large files, `dvc import` does not push imported files to
+any configured remotes for your project by default. This means that when
+`dvc pull/fetch` is run, DVC retrieves imports from their source instead of from
+your remote. It also means that if the source of the import is deleted then the
+files are not backed up in your remote, and data may be lost.
+
+To prevent this, you can use the `--backup` option to request DVC to backup the
+data imports to your project's remote. This also means that `dvc pull/fetch` no
+longer needs to access import sources, so interacts only with the DVC remote,
+and that backed-up imports can be restored just like files that were
+`dvc add`ed.
+
+To update backed-up imports, use `dvc update` like usual.
+
 ## Examples
 
 A simple case for this command is to import a dataset from an external <abbr>DVC

content/docs/user-guide/dvc-files-and-directories.md

@@ -71,6 +71,9 @@ An _output entry_ (`outs`) consists of these fields:
   _checksum_ for HDFS.
 - `cache`: Whether or not this file or directory is <abbr>cached</abbr> (`true`
   by default, if not present). See the `--no-commit` option of `dvc add`.
+- `backup`: Whether or not this file or directory is backed-up to project
+  remotes. (`true` by default for all `outs` except imports, where it is `false`
+  by default).
 
 A _dependency entry_ (`deps`) consists of these fields: