rebase: improve help text

- add a paragraph about default dest/source changesets
- option help: say "changeset" not "revision"
- option help: explain -b/--base better
- clarify that -a/--abort and -c/--continue are different from the
  other options

hgext/rebase.py

@@ -1,506 +1,539
 # rebase.py - rebasing feature for mercurial
 #
 # Copyright 2008 Stefano Tortarolo <stefano.tortarolo at gmail dot com>
 #
 # 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 move sets of revisions to a different ancestor
 
 This extension lets you rebase changesets in an existing Mercurial
 repository.
 
 For more information:
 http://mercurial.selenic.com/wiki/RebaseExtension
 '''
 
 from mercurial import util, repair, merge, cmdutil, commands, error
 from mercurial import extensions, ancestor, copies, patch
 from mercurial.commands import templateopts
 from mercurial.node import nullrev
 from mercurial.lock import release
 from mercurial.i18n import _
 import os, errno
 
 nullmerge = -2
 
 def rebase(ui, repo, **opts):
     """move changeset (and descendants) to a different branch
 
     Rebase uses repeated merging to graft changesets from one part of
-    history onto another. This can be useful for linearizing local
-    changes relative to a master development tree.
+    history (the source) onto another (the destination). This can be
+    useful for linearizing local changes relative to a master
+    development tree.
+
+    If you don't specify a destination changeset (``-d/--dest``),
+    rebase uses the tipmost head of the current named branch as the
+    destination. (The destination changeset is not modified by
+    rebasing, but new changesets are added as its descendants.)
+
+    You can specify which changesets to rebase in two ways: as a
+    \"source\" changeset or as a \"base\" changeset. Both are
+    shorthand for a topologically related set of changesets (the
+    \"source branch\"). If you specify source (``-s/--source``),
+    rebase will rebase that changeset and all of its descendants onto
+    dest. If you specify base (``-b/--base``), rebase will select
+    ancestors of base back to but not including the common ancestor
+    with dest. Thus, ``-b`` is less precise but more convenient than
+    ``-s``: you can specify any changeset in the source branch, and
+    rebase will select the whole branch. If you specify neither ``-s``
+    nor ``-b``, rebase uses the parent of the working directory as the
+    base.
+
+    By default, rebase recreates the changesets in the source branch
+    as descendants of dest and then destroys the originals. Use
+    ``--keep`` to preserve the original source changesets. Some
+    changesets in the source branch (e.g. merges from the destination
+    branch) may be dropped if they no longer contribute any change.
+
+    One result of the rules for selecting the destination changeset
+    and source branch is that, unlike ``merge``, rebase will do
+    nothing if you are at the latest (tipmost) head of a named branch
+    with two heads. You need to explicitly specify source and/or
+    destination (or ``update`` to the other head, if it's the head of
+    the intended source branch).
 
     If a rebase is interrupted to manually resolve a merge, it can be
     continued with --continue/-c or aborted with --abort/-a.
     """
     originalwd = target = None
     external = nullrev
     state = {}
     skipped = set()
     targetancestors = set()
 
     lock = wlock = None
     try:
         lock = repo.lock()
         wlock = repo.wlock()
 
         # Validate input and define rebasing points
         destf = opts.get('dest', None)
         srcf = opts.get('source', None)
         basef = opts.get('base', None)
         contf = opts.get('continue')
         abortf = opts.get('abort')
         collapsef = opts.get('collapse', False)
         extrafn = opts.get('extrafn')
         keepf = opts.get('keep', False)
         keepbranchesf = opts.get('keepbranches', False)
         detachf = opts.get('detach', False)
 
         if contf or abortf:
             if contf and abortf:
                 raise error.ParseError('rebase',
                                        _('cannot use both abort and continue'))
             if collapsef:
                 raise error.ParseError(
                     'rebase', _('cannot use collapse with continue or abort'))
 
             if detachf:
                 raise error.ParseError(
                     'rebase', _('cannot use detach with continue or abort'))
 
             if srcf or basef or destf:
                 raise error.ParseError('rebase',
                     _('abort and continue do not allow specifying revisions'))
 
             (originalwd, target, state, collapsef, keepf,
                                 keepbranchesf, external) = restorestatus(repo)
             if abortf:
                 abort(repo, originalwd, target, state)
                 return
         else:
             if srcf and basef:
                 raise error.ParseError('rebase', _('cannot specify both a '
                                                    'revision and a base'))
             if detachf:
                 if not srcf:
                     raise error.ParseError(
                       'rebase', _('detach requires a revision to be specified'))
                 if basef:
                     raise error.ParseError(
                         'rebase', _('cannot specify a base with detach'))
 
             cmdutil.bail_if_changed(repo)
             result = buildstate(repo, destf, srcf, basef, detachf)
             if not result:
                 # Empty state built, nothing to rebase
                 ui.status(_('nothing to rebase\n'))
                 return
             else:
                 originalwd, target, state = result
                 if collapsef:
                     targetancestors = set(repo.changelog.ancestors(target))
                     external = checkexternal(repo, state, targetancestors)
 
         if keepbranchesf:
             if extrafn:
                 raise error.ParseError(
                     'rebase', _('cannot use both keepbranches and extrafn'))
             def extrafn(ctx, extra):
                 extra['branch'] = ctx.branch()
 
         # Rebase
         if not targetancestors:
             targetancestors = set(repo.changelog.ancestors(target))
             targetancestors.add(target)
 
         for rev in sorted(state):
             if state[rev] == -1:
                 ui.debug("rebasing %d:%s\n" % (rev, repo[rev]))
                 storestatus(repo, originalwd, target, state, collapsef, keepf,
                                                     keepbranchesf, external)
                 p1, p2 = defineparents(repo, rev, target, state,
                                                         targetancestors)
                 if len(repo.parents()) == 2:
                     repo.ui.debug('resuming interrupted rebase\n')
                 else:
                     stats = rebasenode(repo, rev, p1, p2, state)
                     if stats and stats[3] > 0:
                         raise util.Abort(_('fix unresolved conflicts with hg '
                                     'resolve then run hg rebase --continue'))
                 updatedirstate(repo, rev, target, p2)
                 if not collapsef:
                     extra = {'rebase_source': repo[rev].hex()}
                     if extrafn:
                         extrafn(repo[rev], extra)
                     newrev = concludenode(repo, rev, p1, p2, extra=extra)
                 else:
                     # Skip commit if we are collapsing
                     repo.dirstate.setparents(repo[p1].node())
                     newrev = None
                 # Update the state
                 if newrev is not None:
                     state[rev] = repo[newrev].rev()
                 else:
                     if not collapsef:
                         ui.note(_('no changes, revision %d skipped\n') % rev)
                         ui.debug('next revision set to %s\n' % p1)
                         skipped.add(rev)
                     state[rev] = p1
 
         ui.note(_('rebase merging completed\n'))
 
         if collapsef:
             p1, p2 = defineparents(repo, min(state), target,
                                                         state, targetancestors)
             commitmsg = 'Collapsed revision'
             for rebased in state:
                 if rebased not in skipped and state[rebased] != nullmerge:
                     commitmsg += '\n* %s' % repo[rebased].description()
             commitmsg = ui.edit(commitmsg, repo.ui.username())
             newrev = concludenode(repo, rev, p1, external, commitmsg=commitmsg,
                                                     extra=extrafn)
 
         if 'qtip' in repo.tags():
             updatemq(repo, state, skipped, **opts)
 
         if not keepf:
             # Remove no more useful revisions
             rebased = [rev for rev in state if state[rev] != nullmerge]
             if rebased:
                 if set(repo.changelog.descendants(min(rebased))) - set(state):
                     ui.warn(_("warning: new changesets detected "
                               "on source branch, not stripping\n"))
                 else:
                     repair.strip(ui, repo, repo[min(rebased)].node(), "strip")
 
         clearstatus(repo)
         ui.status(_("rebase completed\n"))
         if os.path.exists(repo.sjoin('undo')):
             util.unlink(repo.sjoin('undo'))
         if skipped:
             ui.note(_("%d revisions have been skipped\n") % len(skipped))
     finally:
         release(lock, wlock)
 
 def rebasemerge(repo, rev, first=False):
     'return the correct ancestor'
     oldancestor = ancestor.ancestor
 
     def newancestor(a, b, pfunc):
         if b == rev:
             return repo[rev].parents()[0].rev()
         return oldancestor(a, b, pfunc)
 
     if not first:
         ancestor.ancestor = newancestor
     else:
         repo.ui.debug("first revision, do not change ancestor\n")
     try:
         stats = merge.update(repo, rev, True, True, False)
         return stats
     finally:
         ancestor.ancestor = oldancestor
 
 def checkexternal(repo, state, targetancestors):
     """Check whether one or more external revisions need to be taken in
     consideration. In the latter case, abort.
     """
     external = nullrev
     source = min(state)
     for rev in state:
         if rev == source:
             continue
         # Check externals and fail if there are more than one
         for p in repo[rev].parents():
             if (p.rev() not in state
                         and p.rev() not in targetancestors):
                 if external != nullrev:
                     raise util.Abort(_('unable to collapse, there is more '
                             'than one external parent'))
                 external = p.rev()
     return external
 
 def updatedirstate(repo, rev, p1, p2):
     """Keep track of renamed files in the revision that is going to be rebased
     """
     # Here we simulate the copies and renames in the source changeset
     cop, diver = copies.copies(repo, repo[rev], repo[p1], repo[p2], True)
     m1 = repo[rev].manifest()
     m2 = repo[p1].manifest()
     for k, v in cop.iteritems():
         if k in m1:
             if v in m1 or v in m2:
                 repo.dirstate.copy(v, k)
                 if v in m2 and v not in m1:
                     repo.dirstate.remove(v)
 
 def concludenode(repo, rev, p1, p2, commitmsg=None, extra=None):
     'Commit the changes and store useful information in extra'
     try:
         repo.dirstate.setparents(repo[p1].node(), repo[p2].node())
         if commitmsg is None:
             commitmsg = repo[rev].description()
         if extra is None:
             extra = {}
         # Commit might fail if unresolved files exist
         newrev = repo.commit(text=commitmsg, user=repo[rev].user(),
                              date=repo[rev].date(), extra=extra)
         repo.dirstate.setbranch(repo[newrev].branch())
         return newrev
     except util.Abort:
         # Invalidate the previous setparents
         repo.dirstate.invalidate()
         raise
 
 def rebasenode(repo, rev, p1, p2, state):
     'Rebase a single revision'
     # Merge phase
     # Update to target and merge it with local
     if repo['.'].rev() != repo[p1].rev():
         repo.ui.debug(" update to %d:%s\n" % (repo[p1].rev(), repo[p1]))
         merge.update(repo, p1, False, True, False)
     else:
         repo.ui.debug(" already in target\n")
     repo.dirstate.write()
     repo.ui.debug(" merge against %d:%s\n" % (repo[rev].rev(), repo[rev]))
     first = repo[rev].rev() == repo[min(state)].rev()
     stats = rebasemerge(repo, rev, first)
     return stats
 
 def defineparents(repo, rev, target, state, targetancestors):
     'Return the new parent relationship of the revision that will be rebased'
     parents = repo[rev].parents()
     p1 = p2 = nullrev
 
     P1n = parents[0].rev()
     if P1n in targetancestors:
         p1 = target
     elif P1n in state:
         if state[P1n] == nullmerge:
             p1 = target
         else:
             p1 = state[P1n]
     else: # P1n external
         p1 = target
         p2 = P1n
 
     if len(parents) == 2 and parents[1].rev() not in targetancestors:
         P2n = parents[1].rev()
         # interesting second parent
         if P2n in state:
             if p1 == target: # P1n in targetancestors or external
                 p1 = state[P2n]
             else:
                 p2 = state[P2n]
         else: # P2n external
             if p2 != nullrev: # P1n external too => rev is a merged revision
                 raise util.Abort(_('cannot use revision %d as base, result '
                         'would have 3 parents') % rev)
             p2 = P2n
     repo.ui.debug(" future parents are %d and %d\n" %
                             (repo[p1].rev(), repo[p2].rev()))
     return p1, p2
 
 def isagitpatch(repo, patchname):
     'Return true if the given patch is in git format'
     mqpatch = os.path.join(repo.mq.path, patchname)
     for line in patch.linereader(file(mqpatch, 'rb')):
         if line.startswith('diff --git'):
             return True
     return False
 
 def updatemq(repo, state, skipped, **opts):
     'Update rebased mq patches - finalize and then import them'
     mqrebase = {}
     for p in repo.mq.applied:
         if repo[p.rev].rev() in state:
             repo.ui.debug('revision %d is an mq patch (%s), finalize it.\n' %
                                         (repo[p.rev].rev(), p.name))
             mqrebase[repo[p.rev].rev()] = (p.name, isagitpatch(repo, p.name))
 
     if mqrebase:
         repo.mq.finish(repo, mqrebase.keys())
 
         # We must start import from the newest revision
         for rev in sorted(mqrebase, reverse=True):
             if rev not in skipped:
                 repo.ui.debug('import mq patch %d (%s)\n'
                               % (state[rev], mqrebase[rev][0]))
                 repo.mq.qimport(repo, (), patchname=mqrebase[rev][0],
                             git=mqrebase[rev][1],rev=[str(state[rev])])
         repo.mq.save_dirty()
 
 def storestatus(repo, originalwd, target, state, collapse, keep, keepbranches,
                                                                 external):
     'Store the current status to allow recovery'
     f = repo.opener("rebasestate", "w")
     f.write(repo[originalwd].hex() + '\n')
     f.write(repo[target].hex() + '\n')
     f.write(repo[external].hex() + '\n')
     f.write('%d\n' % int(collapse))
     f.write('%d\n' % int(keep))
     f.write('%d\n' % int(keepbranches))
     for d, v in state.iteritems():
         oldrev = repo[d].hex()
         newrev = repo[v].hex()
         f.write("%s:%s\n" % (oldrev, newrev))
     f.close()
     repo.ui.debug('rebase status stored\n')
 
 def clearstatus(repo):
     'Remove the status files'
     if os.path.exists(repo.join("rebasestate")):
         util.unlink(repo.join("rebasestate"))
 
 def restorestatus(repo):
     'Restore a previously stored status'
     try:
         target = None
         collapse = False
         external = nullrev
         state = {}
         f = repo.opener("rebasestate")
         for i, l in enumerate(f.read().splitlines()):
             if i == 0:
                 originalwd = repo[l].rev()
             elif i == 1:
                 target = repo[l].rev()
             elif i == 2:
                 external = repo[l].rev()
             elif i == 3:
                 collapse = bool(int(l))
             elif i == 4:
                 keep = bool(int(l))
             elif i == 5:
                 keepbranches = bool(int(l))
             else:
                 oldrev, newrev = l.split(':')
                 state[repo[oldrev].rev()] = repo[newrev].rev()
         repo.ui.debug('rebase status resumed\n')
         return originalwd, target, state, collapse, keep, keepbranches, external
     except IOError, err:
         if err.errno != errno.ENOENT:
             raise
         raise util.Abort(_('no rebase in progress'))
 
 def abort(repo, originalwd, target, state):
     'Restore the repository to its original state'
     if set(repo.changelog.descendants(target)) - set(state.values()):
         repo.ui.warn(_("warning: new changesets detected on target branch, "
                                                     "not stripping\n"))
     else:
         # Strip from the first rebased revision
         merge.update(repo, repo[originalwd].rev(), False, True, False)
         rebased = filter(lambda x: x > -1, state.values())
         if rebased:
             strippoint = min(rebased)
             repair.strip(repo.ui, repo, repo[strippoint].node(), "strip")
         clearstatus(repo)
         repo.ui.status(_('rebase aborted\n'))
 
 def buildstate(repo, dest, src, base, detach):
     'Define which revisions are going to be rebased and where'
     targetancestors = set()
     detachset = set()
 
     if not dest:
         # Destination defaults to the latest revision in the current branch
         branch = repo[None].branch()
         dest = repo[branch].rev()
     else:
         if 'qtip' in repo.tags() and (repo[dest].hex() in
                                 [s.rev for s in repo.mq.applied]):
             raise util.Abort(_('cannot rebase onto an applied mq patch'))
         dest = repo[dest].rev()
 
     if src:
         commonbase = repo[src].ancestor(repo[dest])
         if commonbase == repo[src]:
             raise util.Abort(_('source is ancestor of destination'))
         if commonbase == repo[dest]:
             raise util.Abort(_('source is descendant of destination'))
         source = repo[src].rev()
         if detach:
             # We need to keep track of source's ancestors up to the common base
             srcancestors = set(repo.changelog.ancestors(source))
             baseancestors = set(repo.changelog.ancestors(commonbase.rev()))
             detachset = srcancestors - baseancestors
             detachset.remove(commonbase.rev())
     else:
         if base:
             cwd = repo[base].rev()
         else:
             cwd = repo['.'].rev()
 
         if cwd == dest:
             repo.ui.debug('source and destination are the same\n')
             return None
 
         targetancestors = set(repo.changelog.ancestors(dest))
         if cwd in targetancestors:
             repo.ui.debug('source is ancestor of destination\n')
             return None
 
         cwdancestors = set(repo.changelog.ancestors(cwd))
         if dest in cwdancestors:
             repo.ui.debug('source is descendant of destination\n')
             return None
 
         cwdancestors.add(cwd)
         rebasingbranch = cwdancestors - targetancestors
         source = min(rebasingbranch)
 
     repo.ui.debug('rebase onto %d starting from %d\n' % (dest, source))
     state = dict.fromkeys(repo.changelog.descendants(source), nullrev)
     state.update(dict.fromkeys(detachset, nullmerge))
     state[source] = nullrev
     return repo['.'].rev(), repo[dest].rev(), state
 
 def pullrebase(orig, ui, repo, *args, **opts):
     'Call rebase after pull if the latter has been invoked with --rebase'
     if opts.get('rebase'):
         if opts.get('update'):
             del opts['update']
             ui.debug('--update and --rebase are not compatible, ignoring '
                      'the update flag\n')
 
         cmdutil.bail_if_changed(repo)
         revsprepull = len(repo)
         orig(ui, repo, *args, **opts)
         revspostpull = len(repo)
         if revspostpull > revsprepull:
             rebase(ui, repo, **opts)
             branch = repo[None].branch()
             dest = repo[branch].rev()
             if dest != repo['.'].rev():
                 # there was nothing to rebase we force an update
                 merge.update(repo, dest, False, False, False)
     else:
         orig(ui, repo, *args, **opts)
 
 def uisetup(ui):
     'Replace pull with a decorator to provide --rebase option'
     entry = extensions.wrapcommand(commands.table, 'pull', pullrebase)
     entry[1].append(('', 'rebase', None,
                      _("rebase working directory to branch head"))
 )
 
 cmdtable = {
 "rebase":
         (rebase,
         [
-        ('s', 'source', '', _('rebase from a given revision')),
-        ('b', 'base', '', _('rebase from the base of a given revision')),
-        ('d', 'dest', '', _('rebase onto a given revision')),
+        ('s', 'source', '', _('rebase from the specified changeset')),
+        ('b', 'base', '', _('rebase from the base of the specified changeset '
+                            '(up to greatest common ancestor of base and dest)')),
+        ('d', 'dest', '', _('rebase onto the specified changeset')),
         ('', 'collapse', False, _('collapse the rebased changesets')),
         ('', 'keep', False, _('keep original changesets')),
         ('', 'keepbranches', False, _('keep original branch names')),
         ('', 'detach', False, _('force detaching of source from its original '
                                 'branch')),
         ('c', 'continue', False, _('continue an interrupted rebase')),
         ('a', 'abort', False, _('abort an interrupted rebase'))] +
          templateopts,
-        _('hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] '
-                        '[--keep] [--keepbranches] | [-c] | [-a]')),
+        _('hg rebase [-s REV | -b REV] [-d REV] [options]\n'
+          'hg rebase {-a|-c}'))
 }

tests/test-rebase-parameters.out

@@ -1,204 +1,324
 % These fail
 
 % Use continue and abort
 hg rebase: cannot use both abort and continue
-hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] [--keep] [--keepbranches] | [-c] | [-a]
+hg rebase [-s REV | -b REV] [-d REV] [options]
+hg rebase {-a|-c}
 
 move changeset (and descendants) to a different branch
 
     Rebase uses repeated merging to graft changesets from one part of history
-    onto another. This can be useful for linearizing local changes relative to
-    a master development tree.
+    (the source) onto another (the destination). This can be useful for
+    linearizing local changes relative to a master development tree.
+
+    If you don't specify a destination changeset ("-d/--dest"), rebase uses
+    the tipmost head of the current named branch as the destination. (The
+    destination changeset is not modified by rebasing, but new changesets are
+    added as its descendants.)
+
+    You can specify which changesets to rebase in two ways: as a "source"
+    changeset or as a "base" changeset. Both are shorthand for a topologically
+    related set of changesets (the "source branch"). If you specify source
+    ("-s/--source"), rebase will rebase that changeset and all of its
+    descendants onto dest. If you specify base ("-b/--base"), rebase will
+    select ancestors of base back to but not including the common ancestor
+    with dest. Thus, "-b" is less precise but more convenient than "-s": you
+    can specify any changeset in the source branch, and rebase will select the
+    whole branch. If you specify neither "-s" nor "-b", rebase uses the parent
+    of the working directory as the base.
+
+    By default, rebase recreates the changesets in the source branch as
+    descendants of dest and then destroys the originals. Use "--keep" to
+    preserve the original source changesets. Some changesets in the source
+    branch (e.g. merges from the destination branch) may be dropped if they no
+    longer contribute any change.
+
+    One result of the rules for selecting the destination changeset and source
+    branch is that, unlike "merge", rebase will do nothing if you are at the
+    latest (tipmost) head of a named branch with two heads. You need to
+    explicitly specify source and/or destination (or "update" to the other
+    head, if it's the head of the intended source branch).
 
     If a rebase is interrupted to manually resolve a merge, it can be
     continued with --continue/-c or aborted with --abort/-a.
 
 options:
 
- -s --source        rebase from a given revision
- -b --base          rebase from the base of a given revision
- -d --dest          rebase onto a given revision
+ -s --source        rebase from the specified changeset
+ -b --base          rebase from the base of the specified changeset (up to
+                    greatest common ancestor of base and dest)
+ -d --dest          rebase onto the specified changeset
     --collapse      collapse the rebased changesets
     --keep          keep original changesets
     --keepbranches  keep original branch names
     --detach        force detaching of source from its original branch
  -c --continue      continue an interrupted rebase
  -a --abort         abort an interrupted rebase
     --style         display using template map file
     --template      display with template
 
 use "hg -v help rebase" to show global options
 
 % Use continue and collapse
 hg rebase: cannot use collapse with continue or abort
-hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] [--keep] [--keepbranches] | [-c] | [-a]
+hg rebase [-s REV | -b REV] [-d REV] [options]
+hg rebase {-a|-c}
 
 move changeset (and descendants) to a different branch
 
     Rebase uses repeated merging to graft changesets from one part of history
-    onto another. This can be useful for linearizing local changes relative to
-    a master development tree.
+    (the source) onto another (the destination). This can be useful for
+    linearizing local changes relative to a master development tree.
+
+    If you don't specify a destination changeset ("-d/--dest"), rebase uses
+    the tipmost head of the current named branch as the destination. (The
+    destination changeset is not modified by rebasing, but new changesets are
+    added as its descendants.)
+
+    You can specify which changesets to rebase in two ways: as a "source"
+    changeset or as a "base" changeset. Both are shorthand for a topologically
+    related set of changesets (the "source branch"). If you specify source
+    ("-s/--source"), rebase will rebase that changeset and all of its
+    descendants onto dest. If you specify base ("-b/--base"), rebase will
+    select ancestors of base back to but not including the common ancestor
+    with dest. Thus, "-b" is less precise but more convenient than "-s": you
+    can specify any changeset in the source branch, and rebase will select the
+    whole branch. If you specify neither "-s" nor "-b", rebase uses the parent
+    of the working directory as the base.
+
+    By default, rebase recreates the changesets in the source branch as
+    descendants of dest and then destroys the originals. Use "--keep" to
+    preserve the original source changesets. Some changesets in the source
+    branch (e.g. merges from the destination branch) may be dropped if they no
+    longer contribute any change.
+
+    One result of the rules for selecting the destination changeset and source
+    branch is that, unlike "merge", rebase will do nothing if you are at the
+    latest (tipmost) head of a named branch with two heads. You need to
+    explicitly specify source and/or destination (or "update" to the other
+    head, if it's the head of the intended source branch).
 
     If a rebase is interrupted to manually resolve a merge, it can be
     continued with --continue/-c or aborted with --abort/-a.
 
 options:
 
- -s --source        rebase from a given revision
- -b --base          rebase from the base of a given revision
- -d --dest          rebase onto a given revision
+ -s --source        rebase from the specified changeset
+ -b --base          rebase from the base of the specified changeset (up to
+                    greatest common ancestor of base and dest)
+ -d --dest          rebase onto the specified changeset
     --collapse      collapse the rebased changesets
     --keep          keep original changesets
     --keepbranches  keep original branch names
     --detach        force detaching of source from its original branch
  -c --continue      continue an interrupted rebase
  -a --abort         abort an interrupted rebase
     --style         display using template map file
     --template      display with template
 
 use "hg -v help rebase" to show global options
 
 % Use continue/abort and dest/source
 hg rebase: abort and continue do not allow specifying revisions
-hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] [--keep] [--keepbranches] | [-c] | [-a]
+hg rebase [-s REV | -b REV] [-d REV] [options]
+hg rebase {-a|-c}
 
 move changeset (and descendants) to a different branch
 
     Rebase uses repeated merging to graft changesets from one part of history
-    onto another. This can be useful for linearizing local changes relative to
-    a master development tree.
+    (the source) onto another (the destination). This can be useful for
+    linearizing local changes relative to a master development tree.
+
+    If you don't specify a destination changeset ("-d/--dest"), rebase uses
+    the tipmost head of the current named branch as the destination. (The
+    destination changeset is not modified by rebasing, but new changesets are
+    added as its descendants.)
+
+    You can specify which changesets to rebase in two ways: as a "source"
+    changeset or as a "base" changeset. Both are shorthand for a topologically
+    related set of changesets (the "source branch"). If you specify source
+    ("-s/--source"), rebase will rebase that changeset and all of its
+    descendants onto dest. If you specify base ("-b/--base"), rebase will
+    select ancestors of base back to but not including the common ancestor
+    with dest. Thus, "-b" is less precise but more convenient than "-s": you
+    can specify any changeset in the source branch, and rebase will select the
+    whole branch. If you specify neither "-s" nor "-b", rebase uses the parent
+    of the working directory as the base.
+
+    By default, rebase recreates the changesets in the source branch as
+    descendants of dest and then destroys the originals. Use "--keep" to
+    preserve the original source changesets. Some changesets in the source
+    branch (e.g. merges from the destination branch) may be dropped if they no
+    longer contribute any change.
+
+    One result of the rules for selecting the destination changeset and source
+    branch is that, unlike "merge", rebase will do nothing if you are at the
+    latest (tipmost) head of a named branch with two heads. You need to
+    explicitly specify source and/or destination (or "update" to the other
+    head, if it's the head of the intended source branch).
 
     If a rebase is interrupted to manually resolve a merge, it can be
     continued with --continue/-c or aborted with --abort/-a.
 
 options:
 
- -s --source        rebase from a given revision
- -b --base          rebase from the base of a given revision
- -d --dest          rebase onto a given revision
+ -s --source        rebase from the specified changeset
+ -b --base          rebase from the base of the specified changeset (up to
+                    greatest common ancestor of base and dest)
+ -d --dest          rebase onto the specified changeset
     --collapse      collapse the rebased changesets
     --keep          keep original changesets
     --keepbranches  keep original branch names
     --detach        force detaching of source from its original branch
  -c --continue      continue an interrupted rebase
  -a --abort         abort an interrupted rebase
     --style         display using template map file
     --template      display with template
 
 use "hg -v help rebase" to show global options
 
 % Use source and base
 hg rebase: cannot specify both a revision and a base
-hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] [--keep] [--keepbranches] | [-c] | [-a]
+hg rebase [-s REV | -b REV] [-d REV] [options]
+hg rebase {-a|-c}
 
 move changeset (and descendants) to a different branch
 
     Rebase uses repeated merging to graft changesets from one part of history
-    onto another. This can be useful for linearizing local changes relative to
-    a master development tree.
+    (the source) onto another (the destination). This can be useful for
+    linearizing local changes relative to a master development tree.
+
+    If you don't specify a destination changeset ("-d/--dest"), rebase uses
+    the tipmost head of the current named branch as the destination. (The
+    destination changeset is not modified by rebasing, but new changesets are
+    added as its descendants.)
+
+    You can specify which changesets to rebase in two ways: as a "source"
+    changeset or as a "base" changeset. Both are shorthand for a topologically
+    related set of changesets (the "source branch"). If you specify source
+    ("-s/--source"), rebase will rebase that changeset and all of its
+    descendants onto dest. If you specify base ("-b/--base"), rebase will
+    select ancestors of base back to but not including the common ancestor
+    with dest. Thus, "-b" is less precise but more convenient than "-s": you
+    can specify any changeset in the source branch, and rebase will select the
+    whole branch. If you specify neither "-s" nor "-b", rebase uses the parent
+    of the working directory as the base.
+
+    By default, rebase recreates the changesets in the source branch as
+    descendants of dest and then destroys the originals. Use "--keep" to
+    preserve the original source changesets. Some changesets in the source
+    branch (e.g. merges from the destination branch) may be dropped if they no
+    longer contribute any change.
+
+    One result of the rules for selecting the destination changeset and source
+    branch is that, unlike "merge", rebase will do nothing if you are at the
+    latest (tipmost) head of a named branch with two heads. You need to
+    explicitly specify source and/or destination (or "update" to the other
+    head, if it's the head of the intended source branch).
 
     If a rebase is interrupted to manually resolve a merge, it can be
     continued with --continue/-c or aborted with --abort/-a.
 
 options:
 
- -s --source        rebase from a given revision
- -b --base          rebase from the base of a given revision
- -d --dest          rebase onto a given revision
+ -s --source        rebase from the specified changeset
+ -b --base          rebase from the base of the specified changeset (up to
+                    greatest common ancestor of base and dest)
+ -d --dest          rebase onto the specified changeset
     --collapse      collapse the rebased changesets
     --keep          keep original changesets
     --keepbranches  keep original branch names
     --detach        force detaching of source from its original branch
  -c --continue      continue an interrupted rebase
  -a --abort         abort an interrupted rebase
     --style         display using template map file
     --template      display with template
 
 use "hg -v help rebase" to show global options
 
 % Rebase with no arguments - from current
 nothing to rebase
 
 % Rebase with no arguments - from the current branch
 0 files updated, 0 files merged, 1 files removed, 0 files unresolved
 nothing to rebase
 % ----------
 % These work
 
 % Rebase with no arguments (from 3 onto 7)
 3 files updated, 0 files merged, 2 files removed, 0 files unresolved
 saving bundle to 
 adding branch
 adding changesets
 adding manifests
 adding file changes
 added 5 changesets with 5 changes to 5 files
 rebase completed
 % Try to rollback after a rebase (fail)
 no rollback information available
 
 % Rebase with base == '.' => same as no arguments (from 3 onto 7)
 3 files updated, 0 files merged, 3 files removed, 0 files unresolved
 saving bundle to 
 adding branch
 adding changesets
 adding manifests
 adding file changes
 added 5 changesets with 5 changes to 5 files
 rebase completed
 
 % Rebase with dest == default => same as no arguments (from 3 onto 7)
 3 files updated, 0 files merged, 3 files removed, 0 files unresolved
 saving bundle to 
 adding branch
 adding changesets
 adding manifests
 adding file changes
 added 5 changesets with 5 changes to 5 files
 rebase completed
 
 % Specify only source (from 4 onto 7)
 saving bundle to 
 adding branch
 adding changesets
 adding manifests
 adding file changes
 added 4 changesets with 4 changes to 4 files (-1 heads)
 rebase completed
 
 % Specify only dest (from 3 onto 6)
 3 files updated, 0 files merged, 3 files removed, 0 files unresolved
 saving bundle to 
 adding branch
 adding changesets
 adding manifests
 adding file changes
 added 5 changesets with 5 changes to 5 files (+1 heads)
 rebase completed
 
 % Specify only base (from 3 onto 7)
 saving bundle to 
 adding branch
 adding changesets
 adding manifests
 adding file changes
 added 5 changesets with 5 changes to 5 files
 rebase completed
 
 % Specify source and dest (from 4 onto 6)
 saving bundle to 
 adding branch
 adding changesets
 adding manifests
 adding file changes
 added 4 changesets with 4 changes to 4 files
 rebase completed
 
 % Specify base and dest (from 3 onto 6)
 saving bundle to 
 adding branch
 adding changesets
 adding manifests
 adding file changes
 added 5 changesets with 5 changes to 5 files (+1 heads)
 rebase completed