precheck: fix false warning about content-divergence creation

Before this patch, if we try to `hg prune` (without any successors) an
already obsoleted cset which has at least one successor, it would false
warn about new content-divergence. As we know, pruning cset without any
successors can not create any divergence.

Differential Revision: https://phab.mercurial-scm.org/D12002

mercurial/rewriteutil.py

@@ -1,252 +1,258 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
 
 import re
 
 from .i18n import _
 from .node import (
     hex,
     nullrev,
 )
 
 from . import (
     error,
     node,
     obsolete,
     obsutil,
     revset,
     scmutil,
     util,
 )
 
 
 NODE_RE = re.compile(br'\b[0-9a-f]{6,64}\b')
 
 
 def _formatrevs(repo, revs, maxrevs=4):
     """returns a string summarizing revisions in a decent size
 
     If there are few enough revisions, we list them all. Otherwise we display a
     summary of the form:
 
         1ea73414a91b and 5 others
     """
     tonode = repo.changelog.node
     numrevs = len(revs)
     if numrevs < maxrevs:
         shorts = [node.short(tonode(r)) for r in revs]
         summary = b', '.join(shorts)
     else:
         first = revs.first()
         summary = _(b'%s and %d others')
         summary %= (node.short(tonode(first)), numrevs - 1)
     return summary
 
 
-def precheck(repo, revs, action=b'rewrite'):
+def precheck(repo, revs, action=b'rewrite', check_divergence=True):
     """check if revs can be rewritten
     action is used to control the error message.
 
+    check_divergence allows skipping the divergence checks in cases like adding
+    a prune marker (A, ()) to obsstore (which can't be diverging).
+
     Make sure this function is called after taking the lock.
     """
     if nullrev in revs:
         msg = _(b"cannot %s the null revision") % action
         hint = _(b"no changeset checked out")
         raise error.InputError(msg, hint=hint)
 
     if any(util.safehasattr(r, 'rev') for r in revs):
         repo.ui.develwarn(b"rewriteutil.precheck called with ctx not revs")
         revs = (r.rev() for r in revs)
 
     if len(repo[None].parents()) > 1:
         raise error.StateError(
             _(b"cannot %s changesets while merging") % action
         )
 
     publicrevs = repo.revs(b'%ld and public()', revs)
     if publicrevs:
         summary = _formatrevs(repo, publicrevs)
         msg = _(b"cannot %s public changesets: %s") % (action, summary)
         hint = _(b"see 'hg help phases' for details")
         raise error.InputError(msg, hint=hint)
 
     newunstable = disallowednewunstable(repo, revs)
     if newunstable:
         hint = _(b"see 'hg help evolution.instability'")
         raise error.InputError(
             _(b"cannot %s changeset, as that will orphan %d descendants")
             % (action, len(newunstable)),
             hint=hint,
         )
 
+    if not check_divergence:
+        return
+
     if not obsolete.isenabled(repo, obsolete.allowdivergenceopt):
         new_divergence = _find_new_divergence(repo, revs)
         if new_divergence:
             local_ctx, other_ctx, base_ctx = new_divergence
             msg = _(
                 b'cannot %s %s, as that creates content-divergence with %s'
             ) % (
                 action,
                 local_ctx,
                 other_ctx,
             )
             if local_ctx.rev() != base_ctx.rev():
                 msg += _(b', from %s') % base_ctx
             if repo.ui.verbose:
                 if local_ctx.rev() != base_ctx.rev():
                     msg += _(
                         b'\n    changeset %s is a successor of ' b'changeset %s'
                     ) % (local_ctx, base_ctx)
                 msg += _(
                     b'\n    changeset %s already has a successor in '
                     b'changeset %s\n'
                     b'    rewriting changeset %s would create '
                     b'"content-divergence"\n'
                     b'    set experimental.evolution.allowdivergence=True to '
                     b'skip this check'
                 ) % (base_ctx, other_ctx, local_ctx)
                 raise error.InputError(
                     msg,
                     hint=_(
                         b"see 'hg help evolution.instability' for details on content-divergence"
                     ),
                 )
             else:
                 raise error.InputError(
                     msg,
                     hint=_(
                         b"add --verbose for details or see "
                         b"'hg help evolution.instability'"
                     ),
                 )
 
 
 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 _find_new_divergence(repo, revs):
     obsrevs = repo.revs(b'%ld and obsolete()', revs)
     for r in obsrevs:
         div = find_new_divergence_from(repo, repo[r])
         if div:
             return (repo[r], repo[div[0]], repo.unfiltered()[div[1]])
     return None
 
 
 def find_new_divergence_from(repo, ctx):
     """return divergent revision if rewriting an obsolete cset (ctx) will
     create divergence
 
     Returns (<other node>, <common ancestor node>) or None
     """
     if not ctx.obsolete():
         return None
     # We need to check two cases that can cause divergence:
     # case 1: the rev being rewritten has a non-obsolete successor (easily
     #     detected by successorssets)
     sset = obsutil.successorssets(repo, ctx.node())
     if sset:
         return (sset[0][0], ctx.node())
     else:
         # case 2: one of the precursors of the rev being revived has a
         #     non-obsolete successor (we need divergentsets for this)
         divsets = obsutil.divergentsets(repo, ctx)
         if divsets:
             nsuccset = divsets[0][b'divergentnodes']
             prec = divsets[0][b'commonpredecessor']
             return (nsuccset[0], prec)
         return None
 
 
 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)
         )
 
 
 def update_hash_refs(repo, commitmsg, pending=None):
     """Replace all obsolete commit hashes in the message with the current hash.
 
     If the obsolete commit was split or is divergent, the hash is not replaced
     as there's no way to know which successor to choose.
 
     For commands that update a series of commits in the current transaction, the
     new obsolete markers can be considered by setting ``pending`` to a mapping
     of ``pending[oldnode] = [successor_node1, successor_node2,..]``.
     """
     if not pending:
         pending = {}
     cache = {}
     hashes = re.findall(NODE_RE, commitmsg)
     unfi = repo.unfiltered()
     for h in hashes:
         try:
             fullnode = scmutil.resolvehexnodeidprefix(unfi, h)
         except error.WdirUnsupported:
             # Someone has an fffff... in a commit message we're
             # rewriting. Don't try rewriting that.
             continue
         if fullnode is None:
             continue
         ctx = unfi[fullnode]
         if not ctx.obsolete():
             successors = pending.get(fullnode)
             if successors is None:
                 continue
             # obsutil.successorssets() returns a list of list of nodes
             successors = [successors]
         else:
             successors = obsutil.successorssets(repo, ctx.node(), cache=cache)
 
         # We can't make any assumptions about how to update the hash if the
         # cset in question was split or diverged.
         if len(successors) == 1 and len(successors[0]) == 1:
             successor = successors[0][0]
             if successor is not None:
                 newhash = hex(successor)
                 commitmsg = commitmsg.replace(h, newhash[: len(h)])
             else:
                 repo.ui.note(
                     _(
                         b'The stale commit message reference to %s could '
                         b'not be updated\n(The referenced commit was dropped)\n'
                     )
                     % h
                 )
         else:
             repo.ui.note(
                 _(
                     b'The stale commit message reference to %s could '
                     b'not be updated\n'
                 )
                 % h
             )
 
     return commitmsg