shelve: rename 'publicancestors' to something accurate (issue4737)

That function is actually not returning public ancestors at all. This is
pointed by the second line of the docstring...

The bundling behavior was made correct in a5141977198d but with confusion
remaining regarding what each function was doing.

This close issue4737, because this highlight that shelve is actually -not-
bundling too much data (this was actually properly tested).

hgext/shelve.py

@@ -219,8 +219,8 b' def _aborttransaction(repo):'
 def createcmd(ui, repo, pats, opts):
     """subcommand that creates a new shelve"""
 
-    def publicancestors(ctx):
-        """Compute the public ancestors of a commit.
+    def mutableancestors(ctx):
+        """return all mutable ancestors for ctx (included)
 
         Much faster than the revset ancestors(ctx) & draft()"""
         seen = set([nullrev])
@@ -326,7 +326,7 b' def createcmd(ui, repo, pats, opts):'
                 ui.status(_("nothing changed\n"))
             return 1
 
-        bases = list(publicancestors(repo[node]))
+        bases = list(mutableancestors(repo[node]))
         shelvedfile(repo, name, 'hg').writebundle(bases, node)
         cmdutil.export(repo, [node],
                        fp=shelvedfile(repo, name, 'patch').opener('wb'),