Update docs about using multiple -f arguments

Signed-off-by: Daniel Nephin <dnephin@docker.com>

docs/reference/docker-compose.md

@@ -14,7 +14,7 @@ weight=-2
 
 ```
 Usage:
-  docker-compose [options] [COMMAND] [ARGS...]
+  docker-compose [-f=<arg>...] [options] [COMMAND] [ARGS...]
   docker-compose -h|--help
 
 Options:
@@ -41,6 +41,7 @@ Commands:
   unpause            Unpause services
   up                 Create and start containers
   migrate-to-labels  Recreate containers to add labels
+  version            Show the Docker-Compose version information
 ```
 
 The Docker Compose binary. You use this command to build and manage multiple services in Docker containers.
@@ -49,11 +50,18 @@ Use the `-f` flag to specify the location of a Compose configuration file. This
 flag is optional. If you don't provide this flag. Compose looks for a file named
 `docker-compose.yml` in the  working directory. If the file is not found,
 Compose looks in each parent directory successively, until it finds the file.
+If a `docker-compose.override.yml` file is found at the same path as the
+`docker-compose.yml` the contents are merged into the configuration and applied
+as overrides to the `docker-compose.yml`.
 
 Use a `-` as the filename to read configuration file from stdin. When stdin is
 used all paths in the configuration are relative to the current working
 directory.
 
+The `-f` flag may be specified more than once. Each subsequent file will be
+merged into the configuration and applied as an override of the previous set
+of files.
+
 Each configuration can has a project name. If you supply a `-p` flag, you can specify a project name. If you don't specify the flag, Compose uses the current directory name.
 
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