Create an atomic opener that does not automatically rename on close

The revlog.checkinlinesize() uses an atomic opener to replace the
index file after converting it from inline to traditional .i and .d
files.  If this operation is interrupted, the atomic file class can
overwrite a valid file with a partially written one.

This patch introduces an atomic opener that does not automatically
replace the destination file with the tempfile.  This way
an interrupted checkinlinesize() call turns into a noop.

mercurial/revlog.py

@@ -694,7 +694,7 b' class revlog(object):'
             df.write(d)
         fp.close()
         df.close()
-        fp = self.opener(self.indexfile, 'w', atomic=True)
+        fp = self.opener(self.indexfile, 'w', atomictemp=True)
         self.version &= ~(REVLOGNGINLINEDATA)
         if self.count():
             x = self.index[0]
@@ -708,7 +708,9 b' class revlog(object):'
             e = struct.pack(self.indexformat, *x)
             fp.write(e)
 
-        fp.close()
+        # if we don't call rename, the temp file will never replace the
+        # real index
+        fp.rename()
         self.chunkcache = None
 
     def addrevision(self, text, transaction, link, p1=None, p2=None, d=None):

mercurial/util.py

@@ -431,20 +431,33 b' def opener(base, audit=True):'
         os.chmod(temp, st.st_mode)
         return temp
 
-    class atomicfile(file):
-        """the file will only be copied on close"""
-        def __init__(self, name, mode, atomic=False):
+    class atomictempfile(file):
+        """the file will only be copied when rename is called"""
+        def __init__(self, name, mode):
             self.__name = name
             self.temp = mktempcopy(name)
             file.__init__(self, self.temp, mode)
-        def close(self):
+        def rename(self):
             if not self.closed:
                 file.close(self)
                 rename(self.temp, self.__name)
         def __del__(self):
-            self.close()
+            if not self.closed:
+                try:
+                    os.unlink(self.temp)
+                except: pass
+                file.close(self)
 
-    def o(path, mode="r", text=False, atomic=False):
+    class atomicfile(atomictempfile):
+        """the file will only be copied on close"""
+        def __init__(self, name, mode):
+            atomictempfile.__init__(self, name, mode)
+        def close(self):
+            self.rename()
+        def __del__(self):
+            self.rename()
+
+    def o(path, mode="r", text=False, atomic=False, atomictemp=False):
         if audit_p:
             audit_path(path)
         f = os.path.join(p, path)
@@ -462,6 +475,8 b' def opener(base, audit=True):'
             else:
                 if atomic:
                     return atomicfile(f, mode)
+                elif atomictemp:
+                    return atomictempfile(f, mode)
                 if nlink > 1:
                     rename(mktempcopy(f), f)
         return file(f, mode)