Deal with failed clone/transaction interaction

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Deal with failed clone/transaction interaction

> What is happening is that something in the transaction machinery is
> causing the directory to be completely recreated.

The transaction gets rolled back by its destructor. This is critical
so it happens whenever an exception occurs that unwinds the stack.

Unfortunately, what's happening with clone is we're trying to delete
the directory during exception propagation. And a reference to the
transaction is held in the exception backtrace stack frames so it
still exists until the exception is completely resolved.

So there's no way to do the directory delete inside the exception
handling cleanly.

But we can handle it similarly to the transaction itself: use an
object with a destructor.

manifest hash: fc38550a20d64d08333f256bbedc312493c1390b
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mercurial/commands.py

@@ -272,8 +272,6 b' def clone(ui, source, dest = None, **opt'
     """make a copy of an existing repository"""
     source = ui.expandpath(source)
 
-    success = False
-
     if dest is None:
         dest = os.path.basename(os.path.normpath(source))
 
@@ -281,9 +279,19 b' def clone(ui, source, dest = None, **opt'
         ui.warn("abort: destination '%s' already exists\n" % dest)
         return 1
 
-    os.mkdir(dest)
+    class dircleanup:
+        def __init__(self, dir):
+            self.dir = dir
+            os.mkdir(dir)
+        def close(self):
+            self.dir = None
+        def __del__(self):
+            if self.dir:
+                import shutil
+                shutil.rmtree(self.dir, True)
 
-    try:
+    d = dircleanup(dest)
+
         link = 0
         if not source.startswith("http://"):
             d1 = os.stat(dest).st_dev
@@ -314,12 +322,7 b' def clone(ui, source, dest = None, **opt'
         if not opts['noupdate']:
             update(ui, repo)
 
-        success = True
-
-    finally:
-        if not success:
-            import shutil
-            shutil.rmtree(dest, True)
+    d.close()
 
 def commit(ui, repo, *files, **opts):
     """commit the specified files or all outstanding changes"""