shelve: allow unlimited shelved changes per name

Previously, there is a 100 changes limit per name (bookmark or named
branch). And the user will get "too many shelved changes named %s" when they
are trying to shelve the 101th change. I hit that error message today.

This limit was introduced by the shelve extension since the beginning.
The function generating the names was called "gennames", under
"getshelvename".

There is another "gennames" under "backupfilename":

    def backupfilename(self):
        def gennames(base):
            yield base
            base, ext = base.rsplit('.', 1)
            for i in itertools.count(1):
                yield '%s-%d.%s' % (base, i, ext)

"itertools.count" is an endless counter.

Since the other "gennames" generates unlimited number of names, and the
changeset introducing the limit (49d4919d21) does not say why the limit
is useful. It seems safe to just remove the limit.

The format "%02d" was kept intentionally so existing shelved changes won't
break.

hgext/shelve.py

@@ -316,7 +316,7 b' def getshelvename(repo, parent, opts):'
     """Decide on the name this shelve is going to have"""
     def gennames():
         yield label
-        for i in xrange(1, 100):
+        for i in itertools.count(1):
             yield '%s-%02d' % (label, i)
     name = opts.get('name')
     label = repo._activebookmark or parent.branch() or 'default'
@@ -343,8 +343,6 b' def getshelvename(repo, parent, opts):'
             if not shelvedfile(repo, n, patchextension).exists():
                 name = n
                 break
-        else:
-            raise error.Abort(_("too many shelved changes named '%s'") % label)
 
     return name