largefiles: use wlock for lfconvert (issue3444)

largefiles and lfconvert do dirty hacks with dirstate, so to avoid writing that
as a side effect of the wlock release we clear dirstate first.

To avoid confusing lock validation algorithms in error situations we unlock
_before_ removing the target directory.

hgext/largefiles/lfcommands.py

@@ -13,6 +13,7 b' import shutil'
 
 from mercurial import util, match as match_, hg, node, context, error, cmdutil
 from mercurial.i18n import _
+from mercurial.lock import release
 
 import lfutil
 import basestore
@@ -54,10 +55,12 b' def lfconvert(ui, src, dest, *pats, **op'
     rdst = hg.repository(ui, dest, create=True)
 
     success = False
+    dstwlock = dstlock = None
     try:
         # Lock destination to prevent modification while it is converted to.
         # Don't need to lock src because we are just reading from its history
         # which can't change.
+        dstwlock = rdst.wlock()
         dstlock = rdst.lock()
 
         # Get a list of all changesets in the source.  The easy way to do this
@@ -110,10 +113,11 b' def lfconvert(ui, src, dest, *pats, **op'
             ui.progress(_('converting revisions'), None)
         success = True
     finally:
+        rdst.dirstate.clear()
+        release(dstlock, dstwlock)
         if not success:
             # we failed, remove the new directory
             shutil.rmtree(rdst.root)
-        dstlock.release()
 
 def _addchangeset(ui, rsrc, rdst, ctx, revmap):
  # Convert src parents to dst parents