Work on catalog creation.

git_catalog_repository.py

@@ -0,0 +1,40 @@
+# git diff --quiet e5f841bc84d31fee339191a59b8746cb4eb8074c -- ./Aircraft/
+ 
+import subprocess
+import os
+
+class GITCatalogRepository:
+    def __init__(self, path, usesSubmodules = False, singleAircraft = False):
+        self._path = path
+        
+        if !os.path.exists(os.path.join(path, ".git")):
+            raise RuntimeError("not a Git directory:" + path)
+        
+        self._usesSubmodules = usesSubmodules
+        self._singleAircraft = singleAircraft
+        
+        self._currentRevision = subprocess.catch_output(["git", "rev-parse", "HEAD"],
+            cwd = self._path)
+
+    def hasPathChanged(self, path, oldRev):
+        diffArgs = ["git", "diff", "--quiet", oldRev, "--"]
+        if not (self._usesSubmodules and self._singleAircraft):
+            diffArgs.append(path)
+            
+        return subprocess.call(diffArgs, cwd = self._path)
+
+    def update(self):
+        subprocess.call(["git", "pull"])
+        self._currentRevision = subprocess.catch_output(["git", "rev-parse", "HEAD"],
+                cwd = self._path)
+        
+        if self._usesSubmodules:
+            subprocess.call(["git", "submodule", "update"], cwd = self._path)    
+
+    def scmRevisionForPath(self, path):
+        if self._usesSubmodules:
+            return subprocess.catch_output(["git", "rev-parse", "HEAD"], cwd = self._path)
+            
+        return self._currentRevision
+
+