rewriteutil: add utility to check whether empty successors should be skipped

mercurial/rewriteutil.py

@@ -1,55 +1,72 b''
 # rewriteutil.py - utility functions for rewriting changesets
 #
 # Copyright 2017 Octobus <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 from .i18n import _
 
 from . import (
     error,
     node,
     obsolete,
     revset,
 )
 
 
 def precheck(repo, revs, action=b'rewrite'):
     """check if revs can be rewritten
     action is used to control the error message.
 
     Make sure this function is called after taking the lock.
     """
     if node.nullrev in revs:
         msg = _(b"cannot %s null changeset") % action
         hint = _(b"no changeset checked out")
         raise error.Abort(msg, hint=hint)
 
     if len(repo[None].parents()) > 1:
         raise error.Abort(_(b"cannot %s while merging") % action)
 
     publicrevs = repo.revs(b'%ld and public()', revs)
     if publicrevs:
         msg = _(b"cannot %s public changesets") % action
         hint = _(b"see 'hg help phases' for details")
         raise error.Abort(msg, hint=hint)
 
     newunstable = disallowednewunstable(repo, revs)
     if newunstable:
         raise error.Abort(_(b"cannot %s changeset with children") % action)
 
 
 def disallowednewunstable(repo, revs):
     """Checks whether editing the revs will create new unstable changesets and
     are we allowed to create them.
 
     To allow new unstable changesets, set the config:
         `experimental.evolution.allowunstable=True`
     """
     allowunstable = obsolete.isenabled(repo, obsolete.allowunstableopt)
     if allowunstable:
         return revset.baseset()
     return repo.revs(b"(%ld::) - %ld", revs, revs)
+
+
+def skip_empty_successor(ui, command):
+    empty_successor = ui.config(b'rewrite', b'empty-successor')
+    if empty_successor == b'skip':
+        return True
+    elif empty_successor == b'keep':
+        return False
+    else:
+        raise error.ConfigError(
+            _(
+                b"%s doesn't know how to handle config "
+                b"rewrite.empty-successor=%s (only 'skip' and 'keep' are "
+                b"supported)"
+            )
+            % (command, empty_successor)
+        )