convert: introduce hascommitfrommap sink method

Mercurial has stable revision identifiers and rollback and strip. Revisions
referenced in the shamap are thus not necessarily still present but we can
easily check for it.

Subversion do not have stable identifiers and no rollback or strip(?). We must
thus assume that all revisions referenced from a shamap still must be present.

This method is similar to hascommitforsplicemap but different ...

hgext/convert/common.py

@@ -260,6 +260,11 b' class converter_sink(object):'
         """
         pass
 
+    def hascommitfrommap(self, rev):
+        """Return False if a rev mentioned in a filemap is known to not be
+        present."""
+        raise NotImplementedError
+
     def hascommitforsplicemap(self, rev):
         """This method is for the special needs for splicemap handling and not
         for general use. Returns True if the sink contains rev, aborts on some

hgext/convert/hg.py

@@ -253,6 +253,10 b' class mercurial_sink(converter_sink):'
             destmarks[bookmark] = bin(updatedbookmark[bookmark])
         destmarks.write()
 
+    def hascommitfrommap(self, rev):
+        # the exact semantics of clonebranches is unclear so we can't say no
+        return rev in self.repo or self.clonebranches
+
     def hascommitforsplicemap(self, rev):
         if rev not in self.repo and self.clonebranches:
             raise util.Abort(_('revision %s not found in destination '

hgext/convert/subversion.py

@@ -1300,6 +1300,11 b' class svn_sink(converter_sink, commandli'
         self.ui.warn(_('writing Subversion tags is not yet implemented\n'))
         return None, None
 
+    def hascommitfrommap(self, rev):
+        # We trust that revisions referenced in a map still is present
+        # TODO: implement something better if necessary and feasible
+        return True
+
     def hascommitforsplicemap(self, rev):
         # This is not correct as one can convert to an existing subversion
         # repository and childmap would not list all revisions. Too bad.