support for versioning autopkglib and MinimumVersion in recipe keys

- store AUTOPKG_VERSION in env so that it's available for reporting or other purposes (for recipes, metadata, etc.)
- currently version.plist contains a single value that would be manually incremented when new features added
  - would be good in the future to have another patch version that auto-increments with Git commits, ala munkitools

Code/autopkglib/__init__.py

@@ -24,6 +24,7 @@
 import subprocess
 
 from Foundation import CFPreferencesCopyAppValue
+from distutils.version import LooseVersion
 
 BUNDLE_ID = "com.github.autopkg"
 LOCAL_OVERRIDE_KEY = "RecipeInputOverrides"
@@ -210,6 +211,10 @@ def __init__(self, options, env):
         self.env = env
         self.results = []
 
+        version_plist = plistlib.readPlist(
+            os.path.join(os.path.dirname(__file__), "version.plist"))
+        self.env["AUTOPKG_VERSION"] = version_plist["Version"]
+
     def output(msg, verbose_level=1):
         if self.verbose >= verbose_level:
             print msg
@@ -269,6 +274,13 @@ def process_input_overrides(self, recipe, cli_values):
     def verify(self, recipe):
         """Verify a recipe and check for errors."""
 
+        # Check for MinimumAutopkgVersion
+        if "MinimumVersion" in recipe.keys():
+            if LooseVersion(self.env["AUTOPKG_VERSION"]) < LooseVersion(recipe.get("MinimumVersion")):
+                raise AutoPackagerError(
+                        "Recipe requires at least version %s, but we are version %s."
+                        % (recipe.get("MinimumVersion"), self.env["AUTOPKG_VERSION"]))
+
         # Initialize variable set with input variables.
         variables = set(recipe["Input"].keys())
         # Add environment.

Code/autopkglib/version.plist

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>Version</key>
+	<string>0.1.0</string>
+</dict>
+</plist>