Support lines starting with export

lib/dotenv_parser.ex

@@ -20,6 +20,9 @@ defmodule DotenvParser do
   * `\\\\` - Backslash
   * `\\uFFFF` - Unicode escape (4 hex characters to denote the codepoint)
 
+  A line can start with `export ` for easier interoperation with regular shell scripts. These lines are treated the
+  same as any others.
+
   ## Serving suggestion
 
   If you load lots of environment variables in `config/runtime.exs`, you can easily configure them for development by
@@ -38,7 +41,7 @@ defmodule DotenvParser do
   """
 
   @linefeed_re ~R/\r?\n/
-  @line_re ~R/^\s*[a-z_][a-z_0-9]*\s*=/i
+  @line_re ~R/^(?:\s*export)?\s*[a-z_][a-z_0-9]*\s*=/i
   @dquoted_val_re ~R/^\s*"(.*)(?!\\)"\s*(?:#.*)?$/
   @squoted_val_re ~R/^\s*'(.*)(?!\\)'\s*(?:#.*)?$/
   @hex_re ~R/^[0-9a-f]+$/i
@@ -114,7 +117,7 @@ defmodule DotenvParser do
       raise ParseError, "Malformed line cannot be parsed: #{line}"
     else
       [var, val] = String.split(line, "=", parts: 2)
-      var = String.trim(var)
+      var = var |> String.trim() |> String.replace_leading("export ", "")
       val = String.trim(val)
 
       with {:dquoted, nil} <- {:dquoted, Regex.run(@dquoted_val_re, val)},

mix.exs

@@ -4,7 +4,7 @@ defmodule DotenvParser.MixProject do
   def project do
     [
       app: :dotenv_parser,
-      version: "1.0.0",
+      version: "1.1.0",
       elixir: "~> 1.11",
       start_permanent: Mix.env() == :prod,
       deps: deps(),

test/data/.env

@@ -29,3 +29,4 @@ INLINE_COMMENT="foo#bar" # Bark Bark
 INLINE_COMMENT_PLAIN=foo bar # Bark Bark
 END_BACKSLASH="something\" # Comment
 lowercased_var=foo
+export FOO="exports are supported"

test/dotenv_parser_test.exs

@@ -30,7 +30,8 @@ defmodule DotenvParserTest do
              {"INLINE_COMMENT", "foo#bar"},
              {"INLINE_COMMENT_PLAIN", "foo bar"},
              {"END_BACKSLASH", "something\\"},
-             {"lowercased_var", "foo"}
+             {"lowercased_var", "foo"},
+             {"FOO", "exports are supported"}
            ]
   end