win32: backout 1a9ebc83a74c

This change conflicted with TortoiseHg's use of QFileSystemWatcher. Files which
were being monitored (for file-system events) were unable to be reliably updated
using util.atomictempfile.  Often the update would error out in the middle of
the process leaving neither the old or the new file in place.

My guess is that _kernel32.CreateFileA() is triggering an exception that is
not handled correctly within unlink()

mercurial/win32.py

@@ -25,7 +25,6 b' import ctypes, errno, os, subprocess, ra'
 # GetLastError
 _ERROR_SUCCESS = 0
 _ERROR_NO_MORE_FILES = 18
-_ERROR_SHARING_VIOLATION = 32
 _ERROR_INVALID_PARAMETER = 87
 _ERROR_INSUFFICIENT_BUFFER = 122
 
@@ -61,9 +60,7 b' class _BY_HANDLE_FILE_INFORMATION(ctypes'
 
 _OPEN_EXISTING = 3
 
-_FILE_FLAG_OPEN_REPARSE_POINT = 0x00200000
 _FILE_FLAG_BACKUP_SEMANTICS = 0x02000000
-_FILE_FLAG_DELETE_ON_CLOSE = 0x04000000
 
 # SetFileAttributes
 _FILE_ATTRIBUTE_NORMAL = 0x80
@@ -424,18 +421,11 b' def spawndetached(args):'
 def unlink(f):
     '''try to implement POSIX' unlink semantics on Windows'''
 
-    # If we can open f exclusively, no other processes must have open handles
-    # for it and we can expect its name will be deleted immediately when we
-    # close the handle unless we have another in the same process.  We also
-    # expect we shall simply fail to open f if it is a directory.
-    fh = _kernel32.CreateFileA(f, 0, 0, None, _OPEN_EXISTING,
-        _FILE_FLAG_OPEN_REPARSE_POINT | _FILE_FLAG_DELETE_ON_CLOSE, None)
-    if fh != _INVALID_HANDLE_VALUE:
-        _kernel32.CloseHandle(fh)
-        return
-    error = _kernel32.GetLastError()
-    if error != _ERROR_SHARING_VIOLATION:
-        raise ctypes.WinError(error)
+    if os.path.isdir(f):
+        # use EPERM because it is POSIX prescribed value, even though
+        # unlink(2) on directories returns EISDIR on Linux
+        raise IOError(errno.EPERM,
+                      "Unlinking directory not permitted: '%s'" % f)
 
     # POSIX allows to unlink and rename open files. Windows has serious
     # problems with doing that: