Add ability to specify multiple apps from CLI

Author: robertoaloi

Diff for: README.md

@@ -114,6 +114,12 @@ You can use ExDoc via the command line.
    GITHUB_REPO     => ecto
    ```
 
+It is also possible to specify multiple `ebin` directories in the case of _umbrella_ projects:
+
+   ```bash
+   $ ex_doc "PROJECT_NAME" "PROJECT_VERSION" _build/dev/lib/app1/ebin _build/dev/lib/app2/ebin -m "PROJECT_MODULE" -u "https://github.com/GITHUB_USER/GITHUB_REPO" -l path/to/logo.png
+   ```
+
 You can specify a config file via the `--config` option, both Elixir and Erlang formats are supported. Invoke `ex_doc` without arguments to learn more.
 
 <!-- tabs-close -->

Diff for: lib/ex_doc/cli.ex

@@ -69,9 +69,9 @@ defmodule ExDoc.CLI do
   end
 
   defp generate(args, opts, generator) do
-    [project, version, source_beam] = parse_args(args)
+    [project, version | source_beams] = parse_args(args)
 
-    Code.prepend_path(source_beam)
+    Code.prepend_paths(source_beams)
 
     for path <- Keyword.get_values(opts, :paths),
         path <- Path.wildcard(path) do
@@ -80,8 +80,8 @@ defmodule ExDoc.CLI do
 
     opts =
       opts
-      |> Keyword.put(:source_beam, source_beam)
-      |> Keyword.put(:apps, [app(source_beam)])
+      |> Keyword.put(:source_beam, source_beams)
+      |> Keyword.put(:apps, Enum.map(source_beams, &app/1))
       |> merge_config()
       |> normalize_formatters()
 
@@ -166,13 +166,7 @@ defmodule ExDoc.CLI do
     end
   end
 
-  defp parse_args([_project, _version, _source_beam] = args), do: args
-
-  defp parse_args([_, _, _ | _]) do
-    IO.puts("Too many arguments.\n")
-    print_usage()
-    exit({:shutdown, 1})
-  end
+  defp parse_args([_project, _version | _source_beams] = args), do: args
 
   defp parse_args(_) do
     IO.puts("Too few arguments.\n")

Diff for: test/ex_doc/cli_test.exs

@@ -17,7 +17,7 @@ defmodule ExDoc.CLITest do
                 formatter: "html",
                 formatters: ["html", "epub"],
                 apps: [:ex_doc],
-                source_beam: @ebin
+                source_beam: [@ebin]
               ]}
 
     assert epub ==
@@ -26,7 +26,7 @@ defmodule ExDoc.CLITest do
                 formatter: "epub",
                 formatters: ["html", "epub"],
                 apps: [:ex_doc],
-                source_beam: @ebin
+                source_beam: [@ebin]
               ]}
   end
 
@@ -39,7 +39,7 @@ defmodule ExDoc.CLITest do
                 formatter: "epub",
                 formatters: ["epub", "html"],
                 apps: [:ex_doc],
-                source_beam: @ebin
+                source_beam: [@ebin]
               ]}
 
     assert html ==
@@ -48,7 +48,7 @@ defmodule ExDoc.CLITest do
                 formatter: "html",
                 formatters: ["epub", "html"],
                 apps: [:ex_doc],
-                source_beam: @ebin
+                source_beam: [@ebin]
               ]}
   end
 
@@ -60,10 +60,6 @@ defmodule ExDoc.CLITest do
     assert io == "ExDoc v#{ExDoc.version()}\n"
   end
 
-  test "too many arguments" do
-    assert catch_exit(run(["ExDoc", "1.2.3", "/", "kaboom"])) == {:shutdown, 1}
-  end
-
   test "too few arguments" do
     assert catch_exit(run(["ExDoc"])) == {:shutdown, 1}
   end
@@ -98,7 +94,7 @@ defmodule ExDoc.CLITest do
              logo: "logo.png",
              main: "Main",
              output: "html",
-             source_beam: "#{@ebin}",
+             source_beam: ["#{@ebin}"],
              source_ref: "abcdefg",
              source_url: "http://example.com/username/project"
            ]
@@ -127,7 +123,7 @@ defmodule ExDoc.CLITest do
                extras: ["README.md"],
                formatter: "html",
                formatters: ["html"],
-               source_beam: @ebin
+               source_beam: [@ebin]
              ]
     after
       File.rm!("test.exs")
@@ -155,7 +151,7 @@ defmodule ExDoc.CLITest do
                formatter: "html",
                formatters: ["html"],
                logo: "opts_logo.png",
-               source_beam: @ebin
+               source_beam: [@ebin]
              ]
     after
       File.rm!("test.exs")
@@ -192,7 +188,7 @@ defmodule ExDoc.CLITest do
                extras: ["README.md"],
                formatter: "html",
                formatters: ["html"],
-               source_beam: @ebin
+               source_beam: [@ebin]
              ]
     after
       File.rm!("test.config")