transplant: crash if repo.commit() finds nothing to commit

(makes issue2135, issue2264 more obvious, but does nothing to fix
either one)

This seems to happen in two distinct cases:
  * patch.patch() claims success but changes nothing (e.g.
    the transplanted changeset adds an empty file that already
    exists)
  * patch.patch() makes changes, but repo.status() fails to report them

Both of these seem like bugs in other parts of Mercurial, so arguably
it's not transplant's job to detect the failure to commit.  However:
  * detecting the problem as soon as possible is desirable
  * it prevents a more obscure crash later, in transplants.write()
  * there might be other lurking (or future) bugs that cause
    repo.commit() to do nothing

Also, in the case of issue2264 (source changesets silently dropped by
transplant), the only way to spot the problem currently is the crash
in transplants.write().  Failure to transplant a patch should abort
immediately, whether it's user error (patch does not apply) or a
Mercurial bug (e.g. repo.status() failing to report changes).

hgext/transplant.py

@@ -1,611 +1,620 b''
 # Patch transplanting extension for Mercurial
 #
 # Copyright 2006, 2007 Brendan Cully <[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.
 
 '''command to transplant changesets from another branch
 
 This extension allows you to transplant patches from another branch.
 
 Transplanted patches are recorded in .hg/transplant/transplants, as a
 map from a changeset hash to its hash in the source repository.
 '''
 
 from mercurial.i18n import _
 import os, tempfile
 from mercurial import bundlerepo, changegroup, cmdutil, hg, merge, match
 from mercurial import patch, revlog, util, error, discovery
 
 class transplantentry(object):
     def __init__(self, lnode, rnode):
         self.lnode = lnode
         self.rnode = rnode
 
 class transplants(object):
     def __init__(self, path=None, transplantfile=None, opener=None):
         self.path = path
         self.transplantfile = transplantfile
         self.opener = opener
 
         if not opener:
             self.opener = util.opener(self.path)
         self.transplants = []
         self.dirty = False
         self.read()
 
     def read(self):
         abspath = os.path.join(self.path, self.transplantfile)
         if self.transplantfile and os.path.exists(abspath):
             for line in self.opener(self.transplantfile).read().splitlines():
                 lnode, rnode = map(revlog.bin, line.split(':'))
                 self.transplants.append(transplantentry(lnode, rnode))
 
     def write(self):
         if self.dirty and self.transplantfile:
             if not os.path.isdir(self.path):
                 os.mkdir(self.path)
             fp = self.opener(self.transplantfile, 'w')
             for c in self.transplants:
                 l, r = map(revlog.hex, (c.lnode, c.rnode))
                 fp.write(l + ':' + r + '\n')
             fp.close()
         self.dirty = False
 
     def get(self, rnode):
         return [t for t in self.transplants if t.rnode == rnode]
 
     def set(self, lnode, rnode):
         self.transplants.append(transplantentry(lnode, rnode))
         self.dirty = True
 
     def remove(self, transplant):
         del self.transplants[self.transplants.index(transplant)]
         self.dirty = True
 
 class transplanter(object):
     def __init__(self, ui, repo):
         self.ui = ui
         self.path = repo.join('transplant')
         self.opener = util.opener(self.path)
         self.transplants = transplants(self.path, 'transplants',
                                        opener=self.opener)
 
     def applied(self, repo, node, parent):
         '''returns True if a node is already an ancestor of parent
         or has already been transplanted'''
         if hasnode(repo, node):
             if node in repo.changelog.reachable(parent, stop=node):
                 return True
         for t in self.transplants.get(node):
             # it might have been stripped
             if not hasnode(repo, t.lnode):
                 self.transplants.remove(t)
                 return False
             if t.lnode in repo.changelog.reachable(parent, stop=t.lnode):
                 return True
         return False
 
     def apply(self, repo, source, revmap, merges, opts={}):
         '''apply the revisions in revmap one by one in revision order'''
         revs = sorted(revmap)
         p1, p2 = repo.dirstate.parents()
         pulls = []
         diffopts = patch.diffopts(self.ui, opts)
         diffopts.git = True
 
         lock = wlock = None
         try:
             wlock = repo.wlock()
             lock = repo.lock()
             for rev in revs:
                 node = revmap[rev]
                 revstr = '%s:%s' % (rev, revlog.short(node))
 
                 if self.applied(repo, node, p1):
                     self.ui.warn(_('skipping already applied revision %s\n') %
                                  revstr)
                     continue
 
                 parents = source.changelog.parents(node)
                 if not opts.get('filter'):
                     # If the changeset parent is the same as the
                     # wdir's parent, just pull it.
                     if parents[0] == p1:
                         pulls.append(node)
                         p1 = node
                         continue
                     if pulls:
                         if source != repo:
                             repo.pull(source, heads=pulls)
                         merge.update(repo, pulls[-1], False, False, None)
                         p1, p2 = repo.dirstate.parents()
                         pulls = []
 
                 domerge = False
                 if node in merges:
                     # pulling all the merge revs at once would mean we
                     # couldn't transplant after the latest even if
                     # transplants before them fail.
                     domerge = True
                     if not hasnode(repo, node):
                         repo.pull(source, heads=[node])
 
                 if parents[1] != revlog.nullid:
                     self.ui.note(_('skipping merge changeset %s:%s\n')
                                  % (rev, revlog.short(node)))
                     patchfile = None
                 else:
                     fd, patchfile = tempfile.mkstemp(prefix='hg-transplant-')
                     fp = os.fdopen(fd, 'w')
                     gen = patch.diff(source, parents[0], node, opts=diffopts)
                     for chunk in gen:
                         fp.write(chunk)
                     fp.close()
 
                 del revmap[rev]
                 if patchfile or domerge:
                     try:
                         n = self.applyone(repo, node,
                                           source.changelog.read(node),
                                           patchfile, merge=domerge,
                                           log=opts.get('log'),
                                           filter=opts.get('filter'))
                         if n and domerge:
                             self.ui.status(_('%s merged at %s\n') % (revstr,
                                       revlog.short(n)))
                         elif n:
                             self.ui.status(_('%s transplanted to %s\n')
                                            % (revlog.short(node),
                                               revlog.short(n)))
                     finally:
                         if patchfile:
                             os.unlink(patchfile)
             if pulls:
                 repo.pull(source, heads=pulls)
                 merge.update(repo, pulls[-1], False, False, None)
         finally:
             self.saveseries(revmap, merges)
             self.transplants.write()
             lock.release()
             wlock.release()
 
     def filter(self, filter, changelog, patchfile):
         '''arbitrarily rewrite changeset before applying it'''
 
         self.ui.status(_('filtering %s\n') % patchfile)
         user, date, msg = (changelog[1], changelog[2], changelog[4])
 
         fd, headerfile = tempfile.mkstemp(prefix='hg-transplant-')
         fp = os.fdopen(fd, 'w')
         fp.write("# HG changeset patch\n")
         fp.write("# User %s\n" % user)
         fp.write("# Date %d %d\n" % date)
         fp.write(msg + '\n')
         fp.close()
 
         try:
             util.system('%s %s %s' % (filter, util.shellquote(headerfile),
                                    util.shellquote(patchfile)),
                         environ={'HGUSER': changelog[1]},
                         onerr=util.Abort, errprefix=_('filter failed'))
             user, date, msg = self.parselog(file(headerfile))[1:4]
         finally:
             os.unlink(headerfile)
 
         return (user, date, msg)
 
     def applyone(self, repo, node, cl, patchfile, merge=False, log=False,
                  filter=None):
         '''apply the patch in patchfile to the repository as a transplant'''
         (manifest, user, (time, timezone), files, message) = cl[:5]
         date = "%d %d" % (time, timezone)
         extra = {'transplant_source': node}
         if filter:
             (user, date, message) = self.filter(filter, cl, patchfile)
 
         if log:
             # we don't translate messages inserted into commits
             message += '\n(transplanted from %s)' % revlog.hex(node)
 
         self.ui.status(_('applying %s\n') % revlog.short(node))
         self.ui.note('%s %s\n%s\n' % (user, date, message))
 
         if not patchfile and not merge:
             raise util.Abort(_('can only omit patchfile if merging'))
         if patchfile:
             try:
                 files = {}
                 try:
                     patch.patch(patchfile, self.ui, cwd=repo.root,
                                 files=files, eolmode=None)
                     if not files:
                         self.ui.warn(_('%s: empty changeset')
                                      % revlog.hex(node))
                         return None
                 finally:
                     files = patch.updatedir(self.ui, repo, files)
             except Exception, inst:
                 seriespath = os.path.join(self.path, 'series')
                 if os.path.exists(seriespath):
                     os.unlink(seriespath)
                 p1 = repo.dirstate.parents()[0]
                 p2 = node
                 self.log(user, date, message, p1, p2, merge=merge)
                 self.ui.write(str(inst) + '\n')
                 raise util.Abort(_('Fix up the merge and run '
                                    'hg transplant --continue'))
         else:
             files = None
         if merge:
             p1, p2 = repo.dirstate.parents()
             repo.dirstate.setparents(p1, node)
             m = match.always(repo.root, '')
         else:
             m = match.exact(repo.root, '', files)
 
         n = repo.commit(message, user, date, extra=extra, match=m)
+        if not n:
+            # Crash here to prevent an unclear crash later, in
+            # transplants.write().  This can happen if patch.patch()
+            # does nothing but claims success or if repo.status() fails
+            # to report changes done by patch.patch().  These both
+            # appear to be bugs in other parts of Mercurial, but dying
+            # here, as soon as we can detect the problem, is preferable
+            # to silently dropping changesets on the floor.
+            raise RuntimeError('nothing committed after transplant')
         if not merge:
             self.transplants.set(n, node)
 
         return n
 
     def resume(self, repo, source, opts=None):
         '''recover last transaction and apply remaining changesets'''
         if os.path.exists(os.path.join(self.path, 'journal')):
             n, node = self.recover(repo)
             self.ui.status(_('%s transplanted as %s\n') % (revlog.short(node),
                                                            revlog.short(n)))
         seriespath = os.path.join(self.path, 'series')
         if not os.path.exists(seriespath):
             self.transplants.write()
             return
         nodes, merges = self.readseries()
         revmap = {}
         for n in nodes:
             revmap[source.changelog.rev(n)] = n
         os.unlink(seriespath)
 
         self.apply(repo, source, revmap, merges, opts)
 
     def recover(self, repo):
         '''commit working directory using journal metadata'''
         node, user, date, message, parents = self.readlog()
         merge = len(parents) == 2
 
         if not user or not date or not message or not parents[0]:
             raise util.Abort(_('transplant log file is corrupt'))
 
         extra = {'transplant_source': node}
         wlock = repo.wlock()
         try:
             p1, p2 = repo.dirstate.parents()
             if p1 != parents[0]:
                 raise util.Abort(
                     _('working dir not at transplant parent %s') %
                                  revlog.hex(parents[0]))
             if merge:
                 repo.dirstate.setparents(p1, parents[1])
             n = repo.commit(message, user, date, extra=extra)
             if not n:
                 raise util.Abort(_('commit failed'))
             if not merge:
                 self.transplants.set(n, node)
             self.unlog()
 
             return n, node
         finally:
             wlock.release()
 
     def readseries(self):
         nodes = []
         merges = []
         cur = nodes
         for line in self.opener('series').read().splitlines():
             if line.startswith('# Merges'):
                 cur = merges
                 continue
             cur.append(revlog.bin(line))
 
         return (nodes, merges)
 
     def saveseries(self, revmap, merges):
         if not revmap:
             return
 
         if not os.path.isdir(self.path):
             os.mkdir(self.path)
         series = self.opener('series', 'w')
         for rev in sorted(revmap):
             series.write(revlog.hex(revmap[rev]) + '\n')
         if merges:
             series.write('# Merges\n')
             for m in merges:
                 series.write(revlog.hex(m) + '\n')
         series.close()
 
     def parselog(self, fp):
         parents = []
         message = []
         node = revlog.nullid
         inmsg = False
         for line in fp.read().splitlines():
             if inmsg:
                 message.append(line)
             elif line.startswith('# User '):
                 user = line[7:]
             elif line.startswith('# Date '):
                 date = line[7:]
             elif line.startswith('# Node ID '):
                 node = revlog.bin(line[10:])
             elif line.startswith('# Parent '):
                 parents.append(revlog.bin(line[9:]))
             elif not line.startswith('# '):
                 inmsg = True
                 message.append(line)
         return (node, user, date, '\n'.join(message), parents)
 
     def log(self, user, date, message, p1, p2, merge=False):
         '''journal changelog metadata for later recover'''
 
         if not os.path.isdir(self.path):
             os.mkdir(self.path)
         fp = self.opener('journal', 'w')
         fp.write('# User %s\n' % user)
         fp.write('# Date %s\n' % date)
         fp.write('# Node ID %s\n' % revlog.hex(p2))
         fp.write('# Parent ' + revlog.hex(p1) + '\n')
         if merge:
             fp.write('# Parent ' + revlog.hex(p2) + '\n')
         fp.write(message.rstrip() + '\n')
         fp.close()
 
     def readlog(self):
         return self.parselog(self.opener('journal'))
 
     def unlog(self):
         '''remove changelog journal'''
         absdst = os.path.join(self.path, 'journal')
         if os.path.exists(absdst):
             os.unlink(absdst)
 
     def transplantfilter(self, repo, source, root):
         def matchfn(node):
             if self.applied(repo, node, root):
                 return False
             if source.changelog.parents(node)[1] != revlog.nullid:
                 return False
             extra = source.changelog.read(node)[5]
             cnode = extra.get('transplant_source')
             if cnode and self.applied(repo, cnode, root):
                 return False
             return True
 
         return matchfn
 
 def hasnode(repo, node):
     try:
         return repo.changelog.rev(node) != None
     except error.RevlogError:
         return False
 
 def browserevs(ui, repo, nodes, opts):
     '''interactively transplant changesets'''
     def browsehelp(ui):
         ui.write(_('y: transplant this changeset\n'
                    'n: skip this changeset\n'
                    'm: merge at this changeset\n'
                    'p: show patch\n'
                    'c: commit selected changesets\n'
                    'q: cancel transplant\n'
                    '?: show this help\n'))
 
     displayer = cmdutil.show_changeset(ui, repo, opts)
     transplants = []
     merges = []
     for node in nodes:
         displayer.show(repo[node])
         action = None
         while not action:
             action = ui.prompt(_('apply changeset? [ynmpcq?]:'))
             if action == '?':
                 browsehelp(ui)
                 action = None
             elif action == 'p':
                 parent = repo.changelog.parents(node)[0]
                 for chunk in patch.diff(repo, parent, node):
                     ui.write(chunk)
                 action = None
             elif action not in ('y', 'n', 'm', 'c', 'q'):
                 ui.write(_('no such option\n'))
                 action = None
         if action == 'y':
             transplants.append(node)
         elif action == 'm':
             merges.append(node)
         elif action == 'c':
             break
         elif action == 'q':
             transplants = ()
             merges = ()
             break
     displayer.close()
     return (transplants, merges)
 
 def transplant(ui, repo, *revs, **opts):
     '''transplant changesets from another branch
 
     Selected changesets will be applied on top of the current working
     directory with the log of the original changeset. If --log is
     specified, log messages will have a comment appended of the form::
 
       (transplanted from CHANGESETHASH)
 
     You can rewrite the changelog message with the --filter option.
     Its argument will be invoked with the current changelog message as
     $1 and the patch as $2.
 
     If --source/-s is specified, selects changesets from the named
     repository. If --branch/-b is specified, selects changesets from
     the branch holding the named revision, up to that revision. If
     --all/-a is specified, all changesets on the branch will be
     transplanted, otherwise you will be prompted to select the
     changesets you want.
 
     :hg:`transplant --branch REVISION --all` will rebase the selected
     branch (up to the named revision) onto your current working
     directory.
 
     You can optionally mark selected transplanted changesets as merge
     changesets. You will not be prompted to transplant any ancestors
     of a merged transplant, and you can merge descendants of them
     normally instead of transplanting them.
 
     If no merges or revisions are provided, :hg:`transplant` will
     start an interactive changeset browser.
 
     If a changeset application fails, you can fix the merge by hand
     and then resume where you left off by calling :hg:`transplant
     --continue/-c`.
     '''
     def getremotechanges(repo, url):
         sourcerepo = ui.expandpath(url)
         source = hg.repository(ui, sourcerepo)
         tmp = discovery.findcommonincoming(repo, source, force=True)
         common, incoming, rheads = tmp
         if not incoming:
             return (source, None, None)
 
         bundle = None
         if not source.local():
             if source.capable('changegroupsubset'):
                 cg = source.changegroupsubset(incoming, rheads, 'incoming')
             else:
                 cg = source.changegroup(incoming, 'incoming')
             bundle = changegroup.writebundle(cg, None, 'HG10UN')
             source = bundlerepo.bundlerepository(ui, repo.root, bundle)
 
         return (source, incoming, bundle)
 
     def incwalk(repo, incoming, branches, match=util.always):
         if not branches:
             branches = None
         for node in repo.changelog.nodesbetween(incoming, branches)[0]:
             if match(node):
                 yield node
 
     def transplantwalk(repo, root, branches, match=util.always):
         if not branches:
             branches = repo.heads()
         ancestors = []
         for branch in branches:
             ancestors.append(repo.changelog.ancestor(root, branch))
         for node in repo.changelog.nodesbetween(ancestors, branches)[0]:
             if match(node):
                 yield node
 
     def checkopts(opts, revs):
         if opts.get('continue'):
             if opts.get('branch') or opts.get('all') or opts.get('merge'):
                 raise util.Abort(_('--continue is incompatible with '
                                    'branch, all or merge'))
             return
         if not (opts.get('source') or revs or
                 opts.get('merge') or opts.get('branch')):
             raise util.Abort(_('no source URL, branch tag or revision '
                                'list provided'))
         if opts.get('all'):
             if not opts.get('branch'):
                 raise util.Abort(_('--all requires a branch revision'))
             if revs:
                 raise util.Abort(_('--all is incompatible with a '
                                    'revision list'))
 
     checkopts(opts, revs)
 
     if not opts.get('log'):
         opts['log'] = ui.config('transplant', 'log')
     if not opts.get('filter'):
         opts['filter'] = ui.config('transplant', 'filter')
 
     tp = transplanter(ui, repo)
 
     p1, p2 = repo.dirstate.parents()
     if len(repo) > 0 and p1 == revlog.nullid:
         raise util.Abort(_('no revision checked out'))
     if not opts.get('continue'):
         if p2 != revlog.nullid:
             raise util.Abort(_('outstanding uncommitted merges'))
         m, a, r, d = repo.status()[:4]
         if m or a or r or d:
             raise util.Abort(_('outstanding local changes'))
 
     bundle = None
     source = opts.get('source')
     if source:
         (source, incoming, bundle) = getremotechanges(repo, source)
     else:
         source = repo
 
     try:
         if opts.get('continue'):
             tp.resume(repo, source, opts)
             return
 
         tf = tp.transplantfilter(repo, source, p1)
         if opts.get('prune'):
             prune = [source.lookup(r)
                      for r in cmdutil.revrange(source, opts.get('prune'))]
             matchfn = lambda x: tf(x) and x not in prune
         else:
             matchfn = tf
         branches = map(source.lookup, opts.get('branch', ()))
         merges = map(source.lookup, opts.get('merge', ()))
         revmap = {}
         if revs:
             for r in cmdutil.revrange(source, revs):
                 revmap[int(r)] = source.lookup(r)
         elif opts.get('all') or not merges:
             if source != repo:
                 alltransplants = incwalk(source, incoming, branches,
                                          match=matchfn)
             else:
                 alltransplants = transplantwalk(source, p1, branches,
                                                 match=matchfn)
             if opts.get('all'):
                 revs = alltransplants
             else:
                 revs, newmerges = browserevs(ui, source, alltransplants, opts)
                 merges.extend(newmerges)
             for r in revs:
                 revmap[source.changelog.rev(r)] = r
         for r in merges:
             revmap[source.changelog.rev(r)] = r
 
         tp.apply(repo, source, revmap, merges, opts)
     finally:
         if bundle:
             source.close()
             os.unlink(bundle)
 
 cmdtable = {
     "transplant":
         (transplant,
          [('s', 'source', '',
            _('pull patches from REPO'), _('REPO')),
           ('b', 'branch', [],
            _('pull patches from branch BRANCH'), _('BRANCH')),
           ('a', 'all', None, _('pull all changesets up to BRANCH')),
           ('p', 'prune', [],
            _('skip over REV'), _('REV')),
           ('m', 'merge', [],
            _('merge at REV'), _('REV')),
           ('', 'log', None, _('append transplant info to log message')),
           ('c', 'continue', None, _('continue last transplant session '
                                     'after repair')),
           ('', 'filter', '',
            _('filter changesets through command'), _('CMD'))],
          _('hg transplant [-s REPO] [-b BRANCH [-a]] [-p REV] '
            '[-m REV] [REV]...'))
 }