utils/update-checkout: support autostash when pulling

Setting rebase.autostash allows one to do an update-checkout with a
dirty working tree.

Author: Dave Abrahams

test/Prototypes/Integers.swift.gyb

@@ -215,6 +215,11 @@ extension IntegerType {
   }
 }
 
+//===--- SignExtending ----------------------------------------------------===//
+// A SignedIntegerType wrapper over any UnsignedIntegerType; it
+// represents the full width of the unsigned number by adding bits
+// to the representation.
+
 //===--- Homogeneous comparison -------------------------------------------===//
 @_transparent
 @warn_unused_result

utils/update-checkout

@@ -50,7 +50,11 @@ def update_working_copy(repo_path):
         if os.path.isdir(os.path.join(".git", "svn")):
             update_git_svn(repo_path)
         elif os.path.isdir(".git"):
-            check_call([ "git", "pull", "--rebase" ])
+            # Prior to Git 2.6, this is the way to do a "git pull
+            # --rebase" that respects rebase.autostash.  See
+            # http://stackoverflow.com/a/30209750/125349
+            check_call([ "git", "fetch" ])
+            check_call([ "git", "rebase", "FETCH_HEAD" ])
         else:
             check_call([ "svn", "update" ])