show: use consistent (and possibly shorter) node lengths

`hg show` makes heavy use of shortest() to limit the length of the node
hash.

For the "stack" and "work" views, you are often looking at multiple
lines of similar output for "lines" of work. It is visually appeasing
for things to vertically align. A naive use of {shortest(node, N)}
could result in variable length nodes and for the first character of
the description to vary by a column or two.

We implement a function to determine the longest shortest prefix for
a set of revisions. The new function is used to determine the printed
node length for all `hg show` views.

.. feature::

   show: use consistent node length in views

Our previous shortest node length of 5 was arbitrarily chosen.

shortest() already does the work of ensuring that a partial node
isn't ambiguous with an integer revision, which is our primary risk
of a collision for very short nodes. It should be safe to go with the
shortest node possible.

Existing code is also optimized to handle nodes as short as 4.

So, we decrease the minimum hash length from 5 to 4.

We also add a test demonstrating that prefix collisions increase the
node length.

.. feature::

   show: decrease minimum displayed hash length from 5 to 4

Differential Revision: https://phab.mercurial-scm.org/D558

hgext/show.py

@@ -1,439 +1,465 b''
 # show.py - Extension implementing `hg show`
 #
 # Copyright 2017 Gregory Szorc <[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.
 
 """unified command to show various repository information (EXPERIMENTAL)
 
 This extension provides the :hg:`show` command, which provides a central
 command for displaying commonly-accessed repository data and views of that
 data.
 
 The following config options can influence operation.
 
 ``commands``
 ------------
 
 ``show.aliasprefix``
    List of strings that will register aliases for views. e.g. ``s`` will
    effectively set config options ``alias.s<view> = show <view>`` for all
    views. i.e. `hg swork` would execute `hg show work`.
 
    Aliases that would conflict with existing registrations will not be
    performed.
 """
 
 from __future__ import absolute_import
 
 from mercurial.i18n import _
 from mercurial.node import nullrev
 from mercurial import (
     cmdutil,
     commands,
     destutil,
     error,
     formatter,
     graphmod,
     phases,
     pycompat,
     registrar,
     revset,
     revsetlang,
 )
 
 # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
 # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
 # be specifying the version(s) of Mercurial they are tested with, or
 # leave the attribute unspecified.
 testedwith = 'ships-with-hg-core'
 
 cmdtable = {}
 command = registrar.command(cmdtable)
 revsetpredicate = registrar.revsetpredicate()
 
 class showcmdfunc(registrar._funcregistrarbase):
     """Register a function to be invoked for an `hg show <thing>`."""
 
     # Used by _formatdoc().
     _docformat = '%s -- %s'
 
     def _extrasetup(self, name, func, fmtopic=None, csettopic=None):
         """Called with decorator arguments to register a show view.
 
         ``name`` is the sub-command name.
 
         ``func`` is the function being decorated.
 
         ``fmtopic`` is the topic in the style that will be rendered for
         this view.
 
         ``csettopic`` is the topic in the style to be used for a changeset
         printer.
 
         If ``fmtopic`` is specified, the view function will receive a
         formatter instance. If ``csettopic`` is specified, the view
         function will receive a changeset printer.
         """
         func._fmtopic = fmtopic
         func._csettopic = csettopic
 
 showview = showcmdfunc()
 
 @command('show', [
     # TODO: Switch this template flag to use cmdutil.formatteropts if
     # 'hg show' becomes stable before --template/-T is stable. For now,
     # we are putting it here without the '(EXPERIMENTAL)' flag because it
     # is an important part of the 'hg show' user experience and the entire
     # 'hg show' experience is experimental.
     ('T', 'template', '', ('display with template'), _('TEMPLATE')),
     ], _('VIEW'))
 def show(ui, repo, view=None, template=None):
     """show various repository information
 
     A requested view of repository data is displayed.
 
     If no view is requested, the list of available views is shown and the
     command aborts.
 
     .. note::
 
        There are no backwards compatibility guarantees for the output of this
        command. Output may change in any future Mercurial release.
 
        Consumers wanting stable command output should specify a template via
        ``-T/--template``.
 
     List of available views:
     """
     if ui.plain() and not template:
         hint = _('invoke with -T/--template to control output format')
         raise error.Abort(_('must specify a template in plain mode'), hint=hint)
 
     views = showview._table
 
     if not view:
         ui.pager('show')
         # TODO consider using formatter here so available views can be
         # rendered to custom format.
         ui.write(_('available views:\n'))
         ui.write('\n')
 
         for name, func in sorted(views.items()):
             ui.write(('%s\n') % func.__doc__)
 
         ui.write('\n')
         raise error.Abort(_('no view requested'),
                           hint=_('use "hg show VIEW" to choose a view'))
 
     # TODO use same logic as dispatch to perform prefix matching.
     if view not in views:
         raise error.Abort(_('unknown view: %s') % view,
                           hint=_('run "hg show" to see available views'))
 
     template = template or 'show'
 
     fn = views[view]
     ui.pager('show')
 
     if fn._fmtopic:
         fmtopic = 'show%s' % fn._fmtopic
         with ui.formatter(fmtopic, {'template': template}) as fm:
             return fn(ui, repo, fm)
     elif fn._csettopic:
         ref = 'show%s' % fn._csettopic
         spec = formatter.lookuptemplate(ui, ref, template)
         displayer = cmdutil.changeset_templater(ui, repo, spec, buffered=True)
         return fn(ui, repo, displayer)
     else:
         return fn(ui, repo)
 
 @showview('bookmarks', fmtopic='bookmarks')
 def showbookmarks(ui, repo, fm):
     """bookmarks and their associated changeset"""
     marks = repo._bookmarks
     if not len(marks):
         # This is a bit hacky. Ideally, templates would have a way to
         # specify an empty output, but we shouldn't corrupt JSON while
         # waiting for this functionality.
         if not isinstance(fm, formatter.jsonformatter):
             ui.write(_('(no bookmarks set)\n'))
         return
 
+    revs = [repo[node].rev() for node in marks.values()]
     active = repo._activebookmark
     longestname = max(len(b) for b in marks)
-    # TODO consider exposing longest shortest(node).
+    nodelen = longestshortest(repo, revs)
 
     for bm, node in sorted(marks.items()):
         fm.startitem()
         fm.context(ctx=repo[node])
         fm.write('bookmark', '%s', bm)
         fm.write('node', fm.hexfunc(node), fm.hexfunc(node))
         fm.data(active=bm == active,
                 longestbookmarklen=longestname,
-                nodelen=5)
+                nodelen=nodelen)
 
 @showview('stack', csettopic='stack')
 def showstack(ui, repo, displayer):
     """current line of work"""
     wdirctx = repo['.']
     if wdirctx.rev() == nullrev:
         raise error.Abort(_('stack view only available when there is a '
                             'working directory'))
 
     if wdirctx.phase() == phases.public:
         ui.write(_('(empty stack; working directory parent is a published '
                    'changeset)\n'))
         return
 
     # TODO extract "find stack" into a function to facilitate
     # customization and reuse.
 
     baserev = destutil.stackbase(ui, repo)
     basectx = None
 
     if baserev is None:
         baserev = wdirctx.rev()
         stackrevs = {wdirctx.rev()}
     else:
         stackrevs = set(repo.revs('%d::.', baserev))
 
     ctx = repo[baserev]
     if ctx.p1().rev() != nullrev:
         basectx = ctx.p1()
 
     # And relevant descendants.
     branchpointattip = False
     cl = repo.changelog
 
     for rev in cl.descendants([wdirctx.rev()]):
         ctx = repo[rev]
 
         # Will only happen if . is public.
         if ctx.phase() == phases.public:
             break
 
         stackrevs.add(ctx.rev())
 
         # ctx.children() within a function iterating on descandants
         # potentially has severe performance concerns because revlog.children()
         # iterates over all revisions after ctx's node. However, the number of
         # draft changesets should be a reasonably small number. So even if
         # this is quadratic, the perf impact should be minimal.
         if len(ctx.children()) > 1:
             branchpointattip = True
             break
 
     stackrevs = list(sorted(stackrevs, reverse=True))
 
     # Find likely target heads for the current stack. These are likely
     # merge or rebase targets.
     if basectx:
         # TODO make this customizable?
         newheads = set(repo.revs('heads(%d::) - %ld - not public()',
                                  basectx.rev(), stackrevs))
     else:
         newheads = set()
 
+    allrevs = set(stackrevs) | newheads | set([baserev])
+    nodelen = longestshortest(repo, allrevs)
+
     try:
         cmdutil.findcmd('rebase', commands.table)
         haverebase = True
     except (error.AmbiguousCommand, error.UnknownCommand):
         haverebase = False
 
     # TODO use templating.
     # TODO consider using graphmod. But it may not be necessary given
     # our simplicity and the customizations required.
     # TODO use proper graph symbols from graphmod
 
-    shortesttmpl = formatter.maketemplater(ui, '{shortest(node, 5)}')
+    shortesttmpl = formatter.maketemplater(ui, '{shortest(node, %d)}' % nodelen)
     def shortest(ctx):
         return shortesttmpl.render({'ctx': ctx, 'node': ctx.hex()})
 
     # We write out new heads to aid in DAG awareness and to help with decision
     # making on how the stack should be reconciled with commits made since the
     # branch point.
     if newheads:
         # Calculate distance from base so we can render the count and so we can
         # sort display order by commit distance.
         revdistance = {}
         for head in newheads:
             # There is some redundancy in DAG traversal here and therefore
             # room to optimize.
             ancestors = cl.ancestors([head], stoprev=basectx.rev())
             revdistance[head] = len(list(ancestors))
 
         sourcectx = repo[stackrevs[-1]]
 
         sortedheads = sorted(newheads, key=lambda x: revdistance[x],
                              reverse=True)
 
         for i, rev in enumerate(sortedheads):
             ctx = repo[rev]
 
             if i:
                 ui.write(': ')
             else:
                 ui.write('  ')
 
             ui.write(('o  '))
-            displayer.show(ctx, nodelen=5)
+            displayer.show(ctx, nodelen=nodelen)
             displayer.flush(ctx)
             ui.write('\n')
 
             if i:
                 ui.write(':/')
             else:
                 ui.write(' /')
 
             ui.write('    (')
             ui.write(_('%d commits ahead') % revdistance[rev],
                      label='stack.commitdistance')
 
             if haverebase:
                 # TODO may be able to omit --source in some scenarios
                 ui.write('; ')
                 ui.write(('hg rebase --source %s --dest %s' % (
                          shortest(sourcectx), shortest(ctx))),
                          label='stack.rebasehint')
 
             ui.write(')\n')
 
         ui.write(':\n:    ')
         ui.write(_('(stack head)\n'), label='stack.label')
 
     if branchpointattip:
         ui.write(' \\ /  ')
         ui.write(_('(multiple children)\n'), label='stack.label')
         ui.write('  |\n')
 
     for rev in stackrevs:
         ctx = repo[rev]
         symbol = '@' if rev == wdirctx.rev() else 'o'
 
         if newheads:
             ui.write(': ')
         else:
             ui.write('  ')
 
         ui.write(symbol, '  ')
-        displayer.show(ctx, nodelen=5)
+        displayer.show(ctx, nodelen=nodelen)
         displayer.flush(ctx)
         ui.write('\n')
 
     # TODO display histedit hint?
 
     if basectx:
         # Vertically and horizontally separate stack base from parent
         # to reinforce stack boundary.
         if newheads:
             ui.write(':/   ')
         else:
             ui.write(' /   ')
 
         ui.write(_('(stack base)'), '\n', label='stack.label')
         ui.write(('o  '))
 
-        displayer.show(basectx, nodelen=5)
+        displayer.show(basectx, nodelen=nodelen)
         displayer.flush(basectx)
         ui.write('\n')
 
 @revsetpredicate('_underway([commitage[, headage]])')
 def underwayrevset(repo, subset, x):
     args = revset.getargsdict(x, 'underway', 'commitage headage')
     if 'commitage' not in args:
         args['commitage'] = None
     if 'headage' not in args:
         args['headage'] = None
 
     # We assume callers of this revset add a topographical sort on the
     # result. This means there is no benefit to making the revset lazy
     # since the topographical sort needs to consume all revs.
     #
     # With this in mind, we build up the set manually instead of constructing
     # a complex revset. This enables faster execution.
 
     # Mutable changesets (non-public) are the most important changesets
     # to return. ``not public()`` will also pull in obsolete changesets if
     # there is a non-obsolete changeset with obsolete ancestors. This is
     # why we exclude obsolete changesets from this query.
     rs = 'not public() and not obsolete()'
     rsargs = []
     if args['commitage']:
         rs += ' and date(%s)'
         rsargs.append(revsetlang.getstring(args['commitage'],
                                            _('commitage requires a string')))
 
     mutable = repo.revs(rs, *rsargs)
     relevant = revset.baseset(mutable)
 
     # Add parents of mutable changesets to provide context.
     relevant += repo.revs('parents(%ld)', mutable)
 
     # We also pull in (public) heads if they a) aren't closing a branch
     # b) are recent.
     rs = 'head() and not closed()'
     rsargs = []
     if args['headage']:
         rs += ' and date(%s)'
         rsargs.append(revsetlang.getstring(args['headage'],
                                            _('headage requires a string')))
 
     relevant += repo.revs(rs, *rsargs)
 
     # Add working directory parent.
     wdirrev = repo['.'].rev()
     if wdirrev != nullrev:
         relevant += revset.baseset({wdirrev})
 
     return subset & relevant
 
 @showview('work', csettopic='work')
 def showwork(ui, repo, displayer):
     """changesets that aren't finished"""
     # TODO support date-based limiting when calling revset.
     revs = repo.revs('sort(_underway(), topo)')
+    nodelen = longestshortest(repo, revs)
 
     revdag = graphmod.dagwalker(repo, revs)
 
     ui.setconfig('experimental', 'graphshorten', True)
     cmdutil.displaygraph(ui, repo, revdag, displayer, graphmod.asciiedges,
-                         props={'nodelen': 5})
+                         props={'nodelen': nodelen})
 
 def extsetup(ui):
     # Alias `hg <prefix><view>` to `hg show <view>`.
     for prefix in ui.configlist('commands', 'show.aliasprefix'):
         for view in showview._table:
             name = '%s%s' % (prefix, view)
 
             choice, allcommands = cmdutil.findpossible(name, commands.table,
                                                        strict=True)
 
             # This alias is already a command name. Don't set it.
             if name in choice:
                 continue
 
             # Same for aliases.
             if ui.config('alias', name):
                 continue
 
             ui.setconfig('alias', name, 'show %s' % view, source='show')
 
+def longestshortest(repo, revs, minlen=4):
+    """Return the length of the longest shortest node to identify revisions.
+
+    The result of this function can be used with the ``shortest()`` template
+    function to ensure that a value is unique and unambiguous for a given
+    set of nodes.
+
+    The number of revisions in the repo is taken into account to prevent
+    a numeric node prefix from conflicting with an integer revision number.
+    If we fail to do this, a value of e.g. ``10023`` could mean either
+    revision 10023 or node ``10023abc...``.
+    """
+    tmpl = formatter.maketemplater(repo.ui, '{shortest(node, %d)}' % minlen)
+    lens = [minlen]
+    for rev in revs:
+        ctx = repo[rev]
+        shortest = tmpl.render({'ctx': ctx, 'node': ctx.hex()})
+        lens.append(len(shortest))
+
+    return max(lens)
+
 # Adjust the docstring of the show command so it shows all registered views.
 # This is a bit hacky because it runs at the end of module load. When moved
 # into core or when another extension wants to provide a view, we'll need
 # to do this more robustly.
 # TODO make this more robust.
 def _updatedocstring():
     longest = max(map(len, showview._table.keys()))
     entries = []
     for key in sorted(showview._table.keys()):
         entries.append(pycompat.sysstr('    %s   %s' % (
             key.ljust(longest), showview._table[key]._origdoc)))
 
     cmdtable['show'][0].__doc__ = pycompat.sysstr('%s\n\n%s\n    ') % (
         cmdtable['show'][0].__doc__.rstrip(),
         pycompat.sysstr('\n\n').join(entries))
 
 _updatedocstring()

tests/test-show-stack.t

@@ -1,220 +1,220 b''
   $ cat >> $HGRCPATH << EOF
   > [extensions]
   > show =
   > EOF
 
   $ hg init repo0
   $ cd repo0
 
 Empty repo / no checkout results in error
 
   $ hg show stack
   abort: stack view only available when there is a working directory
   [255]
 
 Stack displays single draft changeset as root revision
 
   $ echo 0 > foo
   $ hg -q commit -A -m 'commit 0'
   $ hg show stack
-    @  9f171 commit 0
+    @  9f17 commit 0
 
 Stack displays multiple draft changesets
 
   $ echo 1 > foo
   $ hg commit -m 'commit 1'
   $ echo 2 > foo
   $ hg commit -m 'commit 2'
   $ echo 3 > foo
   $ hg commit -m 'commit 3'
   $ echo 4 > foo
   $ hg commit -m 'commit 4'
   $ hg show stack
-    @  2737b commit 4
-    o  d1a69 commit 3
-    o  128c8 commit 2
-    o  181cc commit 1
-    o  9f171 commit 0
+    @  2737 commit 4
+    o  d1a6 commit 3
+    o  128c commit 2
+    o  181c commit 1
+    o  9f17 commit 0
 
 Public parent of draft base is displayed, separated from stack
 
   $ hg phase --public -r 0
   $ hg show stack
-    @  2737b commit 4
-    o  d1a69 commit 3
-    o  128c8 commit 2
-    o  181cc commit 1
+    @  2737 commit 4
+    o  d1a6 commit 3
+    o  128c commit 2
+    o  181c commit 1
    /   (stack base)
-  o  9f171 commit 0
+  o  9f17 commit 0
 
   $ hg phase --public -r 1
   $ hg show stack
-    @  2737b commit 4
-    o  d1a69 commit 3
-    o  128c8 commit 2
+    @  2737 commit 4
+    o  d1a6 commit 3
+    o  128c commit 2
    /   (stack base)
-  o  181cc commit 1
+  o  181c commit 1
 
 Draft descendants are shown
 
   $ hg -q up 2
   $ hg show stack
-    o  2737b commit 4
-    o  d1a69 commit 3
-    @  128c8 commit 2
+    o  2737 commit 4
+    o  d1a6 commit 3
+    @  128c commit 2
    /   (stack base)
-  o  181cc commit 1
+  o  181c commit 1
 
   $ hg -q up 3
   $ hg show stack
-    o  2737b commit 4
-    @  d1a69 commit 3
-    o  128c8 commit 2
+    o  2737 commit 4
+    @  d1a6 commit 3
+    o  128c commit 2
    /   (stack base)
-  o  181cc commit 1
+  o  181c commit 1
 
 working dir on public changeset should display special message
 
   $ hg -q up 1
   $ hg show stack
   (empty stack; working directory parent is a published changeset)
 
 Branch point in descendants displayed at top of graph
 
   $ hg -q up 3
   $ echo b > foo
   $ hg commit -m 'commit 5 (new dag branch)'
   created new head
   $ hg -q up 2
   $ hg show stack
    \ /  (multiple children)
     |
-    o  d1a69 commit 3
-    @  128c8 commit 2
+    o  d1a6 commit 3
+    @  128c commit 2
    /   (stack base)
-  o  181cc commit 1
+  o  181c commit 1
 
   $ cd ..
 
 Base is stopped at merges
 
   $ hg init merge-base
   $ cd merge-base
   $ echo 0 > foo
   $ hg -q commit -A -m initial
   $ echo h1 > foo
   $ hg commit -m 'head 1'
   $ hg -q up 0
   $ echo h2 > foo
   $ hg -q commit -m 'head 2'
   $ hg phase --public -r 0:tip
   $ hg -q up 1
   $ hg merge -t :local 2
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   $ hg commit -m 'merge heads'
 
 TODO doesn't yet handle case where wdir is a draft merge
 
   $ hg show stack
-    @  8ee90 merge heads
+    @  8ee9 merge heads
    /   (stack base)
-  o  59478 head 1
+  o  5947 head 1
 
   $ echo d1 > foo
   $ hg commit -m 'draft 1'
   $ echo d2 > foo
   $ hg commit -m 'draft 2'
 
   $ hg show stack
-    @  430d5 draft 2
-    o  787b1 draft 1
+    @  430d draft 2
+    o  787b draft 1
    /   (stack base)
-  o  8ee90 merge heads
+  o  8ee9 merge heads
 
   $ cd ..
 
 Now move on to stacks when there are more commits after the base branchpoint
 
   $ hg init public-rebase
   $ cd public-rebase
   $ echo 0 > foo
   $ hg -q commit -A -m 'base'
   $ hg phase --public -r .
   $ echo d1 > foo
   $ hg commit -m 'draft 1'
   $ echo d2 > foo
   $ hg commit -m 'draft 2'
   $ hg -q up 0
   $ echo 1 > foo
   $ hg commit -m 'new 1'
   created new head
   $ echo 2 > foo
   $ hg commit -m 'new 2'
   $ hg -q up 2
 
 Newer draft heads don't impact output
 
   $ hg show stack
-    @  eaffc draft 2
-    o  2b218 draft 1
+    @  eaff draft 2
+    o  2b21 draft 1
    /   (stack base)
-  o  b66bb base
+  o  b66b base
 
 Newer public heads are rendered
 
   $ hg phase --public -r '::tip'
 
   $ hg show stack
-    o  baa4b new 2
+    o  baa4 new 2
    /    (2 commits ahead)
   :
   :    (stack head)
-  : @  eaffc draft 2
-  : o  2b218 draft 1
+  : @  eaff draft 2
+  : o  2b21 draft 1
   :/   (stack base)
-  o  b66bb base
+  o  b66b base
 
 If rebase is available, we show a hint how to rebase to that head
 
   $ hg --config extensions.rebase= show stack
-    o  baa4b new 2
-   /    (2 commits ahead; hg rebase --source 2b218 --dest baa4b)
+    o  baa4 new 2
+   /    (2 commits ahead; hg rebase --source 2b21 --dest baa4)
   :
   :    (stack head)
-  : @  eaffc draft 2
-  : o  2b218 draft 1
+  : @  eaff draft 2
+  : o  2b21 draft 1
   :/   (stack base)
-  o  b66bb base
+  o  b66b base
 
 Similar tests but for multiple heads
 
   $ hg -q up 0
   $ echo h2 > foo
   $ hg -q commit -m 'new head 2'
   $ hg phase --public -r .
   $ hg -q up 2
 
   $ hg show stack
-    o  baa4b new 2
+    o  baa4 new 2
    /    (2 commits ahead)
-  : o  9a848 new head 2
+  : o  9a84 new head 2
   :/    (1 commits ahead)
   :
   :    (stack head)
-  : @  eaffc draft 2
-  : o  2b218 draft 1
+  : @  eaff draft 2
+  : o  2b21 draft 1
   :/   (stack base)
-  o  b66bb base
+  o  b66b base
 
   $ hg --config extensions.rebase= show stack
-    o  baa4b new 2
-   /    (2 commits ahead; hg rebase --source 2b218 --dest baa4b)
-  : o  9a848 new head 2
-  :/    (1 commits ahead; hg rebase --source 2b218 --dest 9a848)
+    o  baa4 new 2
+   /    (2 commits ahead; hg rebase --source 2b21 --dest baa4)
+  : o  9a84 new head 2
+  :/    (1 commits ahead; hg rebase --source 2b21 --dest 9a84)
   :
   :    (stack head)
-  : @  eaffc draft 2
-  : o  2b218 draft 1
+  : @  eaff draft 2
+  : o  2b21 draft 1
   :/   (stack base)
-  o  b66bb base
+  o  b66b base

tests/test-show-work.t

@@ -1,237 +1,267 b''
   $ cat >> $HGRCPATH << EOF
   > [extensions]
   > show =
   > EOF
 
   $ hg init repo0
   $ cd repo0
 
 Command works on an empty repo
 
   $ hg show work
 
 Single draft changeset shown
 
   $ echo 0 > foo
   $ hg -q commit -A -m 'commit 0'
 
   $ hg show work
-  @  9f171 commit 0
+  @  9f17 commit 0
 
 Even when it isn't the wdir
 
   $ hg -q up null
 
   $ hg show work
-  o  9f171 commit 0
+  o  9f17 commit 0
 
 Single changeset is still there when public because it is a head
 
   $ hg phase --public -r 0
   $ hg show work
-  o  9f171 commit 0
+  o  9f17 commit 0
 
 A draft child will show both it and public parent
 
   $ hg -q up 0
   $ echo 1 > foo
   $ hg commit -m 'commit 1'
 
   $ hg show work
-  @  181cc commit 1
-  o  9f171 commit 0
+  @  181c commit 1
+  o  9f17 commit 0
 
 Multiple draft children will be shown
 
   $ echo 2 > foo
   $ hg commit -m 'commit 2'
 
   $ hg show work
-  @  128c8 commit 2
-  o  181cc commit 1
-  o  9f171 commit 0
+  @  128c commit 2
+  o  181c commit 1
+  o  9f17 commit 0
 
 Bumping first draft changeset to public will hide its parent
 
   $ hg phase --public -r 1
   $ hg show work
-  @  128c8 commit 2
-  o  181cc commit 1
+  @  128c commit 2
+  o  181c commit 1
   |
   ~
 
 Multiple DAG heads will be shown
 
   $ hg -q up -r 1
   $ echo 3 > foo
   $ hg commit -m 'commit 3'
   created new head
 
   $ hg show work
-  @  f0abc commit 3
-  | o  128c8 commit 2
+  @  f0ab commit 3
+  | o  128c commit 2
   |/
-  o  181cc commit 1
+  o  181c commit 1
   |
   ~
 
 Even when wdir is something else
 
   $ hg -q up null
 
   $ hg show work
-  o  f0abc commit 3
-  | o  128c8 commit 2
+  o  f0ab commit 3
+  | o  128c commit 2
   |/
-  o  181cc commit 1
+  o  181c commit 1
   |
   ~
 
 Draft child shows public head (multiple heads)
 
   $ hg -q up 0
   $ echo 4 > foo
   $ hg commit -m 'commit 4'
   created new head
 
   $ hg show work
-  @  668ca commit 4
-  | o  f0abc commit 3
-  | | o  128c8 commit 2
+  @  668c commit 4
+  | o  f0ab commit 3
+  | | o  128c commit 2
   | |/
-  | o  181cc commit 1
+  | o  181c commit 1
   |/
-  o  9f171 commit 0
+  o  9f17 commit 0
 
   $ cd ..
 
 Branch name appears in output
 
   $ hg init branches
   $ cd branches
   $ echo 0 > foo
   $ hg -q commit -A -m 'commit 0'
   $ echo 1 > foo
   $ hg commit -m 'commit 1'
   $ echo 2 > foo
   $ hg commit -m 'commit 2'
   $ hg phase --public -r .
   $ hg -q up -r 1
   $ hg branch mybranch
   marked working directory as branch mybranch
   (branches are permanent and global, did you want a bookmark?)
   $ echo 3 > foo
   $ hg commit -m 'commit 3'
   $ echo 4 > foo
   $ hg commit -m 'commit 4'
 
   $ hg show work
-  @  f8dd3 (mybranch) commit 4
-  o  90cfc (mybranch) commit 3
-  | o  128c8 commit 2
+  @  f8dd (mybranch) commit 4
+  o  90cf (mybranch) commit 3
+  | o  128c commit 2
   |/
-  o  181cc commit 1
+  o  181c commit 1
   |
   ~
 
   $ cd ..
 
 Bookmark name appears in output
 
   $ hg init bookmarks
   $ cd bookmarks
   $ echo 0 > foo
   $ hg -q commit -A -m 'commit 0'
   $ echo 1 > foo
   $ hg commit -m 'commit 1'
   $ echo 2 > foo
   $ hg commit -m 'commit 2'
   $ hg phase --public -r .
   $ hg bookmark @
   $ hg -q up -r 1
   $ echo 3 > foo
   $ hg commit -m 'commit 3'
   created new head
   $ echo 4 > foo
   $ hg commit -m 'commit 4'
   $ hg bookmark mybook
 
   $ hg show work
-  @  cac82 (mybook) commit 4
-  o  f0abc commit 3
-  | o  128c8 (@) commit 2
+  @  cac8 (mybook) commit 4
+  o  f0ab commit 3
+  | o  128c (@) commit 2
   |/
-  o  181cc commit 1
+  o  181c commit 1
   |
   ~
 
   $ cd ..
 
 Tags are rendered
 
   $ hg init tags
   $ cd tags
   $ echo 0 > foo
   $ hg -q commit -A -m 'commit 1'
   $ echo 1 > foo
   $ hg commit -m 'commit 2'
   $ hg tag 0.1
   $ hg phase --public -r .
   $ echo 2 > foo
   $ hg commit -m 'commit 3'
   $ hg tag 0.2
 
   $ hg show work
-  @  37582 Added tag 0.2 for changeset 6379c25b76f1
-  o  6379c (0.2) commit 3
-  o  a2ad9 Added tag 0.1 for changeset 6a75536ea0b1
+  @  3758 Added tag 0.2 for changeset 6379c25b76f1
+  o  6379 (0.2) commit 3
+  o  a2ad Added tag 0.1 for changeset 6a75536ea0b1
   |
   ~
 
   $ cd ..
 
 Multiple names on same changeset render properly
 
   $ hg init multiplenames
   $ cd multiplenames
   $ echo 0 > foo
   $ hg -q commit -A -m 'commit 1'
   $ hg phase --public -r .
   $ hg branch mybranch
   marked working directory as branch mybranch
   (branches are permanent and global, did you want a bookmark?)
   $ hg bookmark mybook
   $ echo 1 > foo
   $ hg commit -m 'commit 2'
 
   $ hg show work
-  @  34834 (mybook) (mybranch) commit 2
-  o  97fcc commit 1
+  @  3483 (mybook) (mybranch) commit 2
+  o  97fc commit 1
 
 Multiple bookmarks on same changeset render properly
 
   $ hg book mybook2
   $ hg show work
-  @  34834 (mybook mybook2) (mybranch) commit 2
-  o  97fcc commit 1
+  @  3483 (mybook mybook2) (mybranch) commit 2
+  o  97fc commit 1
 
   $ cd ..
 
 Extra namespaces are rendered
 
   $ hg init extranamespaces
   $ cd extranamespaces
   $ echo 0 > foo
   $ hg -q commit -A -m 'commit 1'
   $ hg phase --public -r .
   $ echo 1 > foo
   $ hg commit -m 'commit 2'
   $ echo 2 > foo
   $ hg commit -m 'commit 3'
 
   $ hg --config extensions.revnames=$TESTDIR/revnamesext.py show work
-  @  32f3e (r2) commit 3
-  o  6a755 (r1) commit 2
-  o  97fcc (r0) commit 1
+  @  32f3 (r2) commit 3
+  o  6a75 (r1) commit 2
+  o  97fc (r0) commit 1
 
   $ cd ..
+
+Prefix collision on hashes increases shortest node length
+
+  $ hg init hashcollision
+  $ cd hashcollision
+  $ echo 0 > a
+  $ hg -q commit -Am 0
+  $ for i in 17 1057 2857 4025; do
+  >   hg -q up 0
+  >   echo $i > a
+  >   hg -q commit -m $i
+  >   echo 0 > a
+  >   hg commit -m "$i commit 2"
+  > done
+
+  $ hg show work
+  @  cfd04 4025 commit 2
+  o  c562d 4025
+  | o  08048 2857 commit 2
+  | o  c5623 2857
+  |/
+  | o  6a6b6 1057 commit 2
+  | o  c5625 1057
+  |/
+  | o  96b4e 17 commit 2
+  | o  11424 17
+  |/
+  o  b4e73 0
+
+  $ cd ..

tests/test-show.t

@@ -1,173 +1,173 b''
   $ cat >> $HGRCPATH << EOF
   > [extensions]
   > show =
   > EOF
 
 No arguments shows available views
 
   $ hg init empty
   $ cd empty
   $ hg show
   available views:
   
   bookmarks -- bookmarks and their associated changeset
   stack -- current line of work
   work -- changesets that aren't finished
   
   abort: no view requested
   (use "hg show VIEW" to choose a view)
   [255]
 
 `hg help show` prints available views
 
   $ hg help show
   hg show VIEW
   
   show various repository information
   
       A requested view of repository data is displayed.
   
       If no view is requested, the list of available views is shown and the
       command aborts.
   
       Note:
          There are no backwards compatibility guarantees for the output of this
          command. Output may change in any future Mercurial release.
   
          Consumers wanting stable command output should specify a template via
          "-T/--template".
   
       List of available views:
   
       bookmarks   bookmarks and their associated changeset
   
       stack       current line of work
   
       work        changesets that aren't finished
   
   (use 'hg help -e show' to show help for the show extension)
   
   options:
   
    -T --template TEMPLATE display with template
   
   (some details hidden, use --verbose to show complete help)
 
 Unknown view prints error
 
   $ hg show badview
   abort: unknown view: badview
   (run "hg show" to see available views)
   [255]
 
 HGPLAIN results in abort
 
   $ HGPLAIN=1 hg show bookmarks
   abort: must specify a template in plain mode
   (invoke with -T/--template to control output format)
   [255]
 
 But not if a template is specified
 
   $ HGPLAIN=1 hg show bookmarks -T '{bookmark}\n'
   (no bookmarks set)
 
   $ cd ..
 
 bookmarks view with no bookmarks prints empty message
 
   $ hg init books
   $ cd books
   $ touch f0
   $ hg -q commit -A -m initial
 
   $ hg show bookmarks
   (no bookmarks set)
 
 bookmarks view shows bookmarks in an aligned table
 
   $ echo book1 > f0
   $ hg commit -m 'commit for book1'
   $ echo book2 > f0
   $ hg commit -m 'commit for book2'
 
   $ hg bookmark -r 1 book1
   $ hg bookmark a-longer-bookmark
 
   $ hg show bookmarks
-  * a-longer-bookmark    7b570
-    book1                b757f
+  * a-longer-bookmark    7b57
+    book1                b757
 
 A custom bookmarks template works
 
   $ hg show bookmarks -T '{node} {bookmark} {active}\n'
   7b5709ab64cbc34da9b4367b64afff47f2c4ee83 a-longer-bookmark True
   b757f780b8ffd71267c6ccb32e0882d9d32a8cc0 book1 False
 
 bookmarks JSON works
 
   $ hg show bookmarks -T json
   [
    {
     "active": true,
     "bookmark": "a-longer-bookmark",
     "longestbookmarklen": 17,
     "node": "7b5709ab64cbc34da9b4367b64afff47f2c4ee83",
-    "nodelen": 5
+    "nodelen": 4
    },
    {
     "active": false,
     "bookmark": "book1",
     "longestbookmarklen": 17,
     "node": "b757f780b8ffd71267c6ccb32e0882d9d32a8cc0",
-    "nodelen": 5
+    "nodelen": 4
    }
   ]
 
 JSON works with no bookmarks
 
   $ hg book -d a-longer-bookmark
   $ hg book -d book1
   $ hg show bookmarks -T json
   [
   ]
 
 commands.show.aliasprefix aliases values to `show <view>`
 
   $ hg --config commands.show.aliasprefix=s sbookmarks
   (no bookmarks set)
 
   $ hg --config commands.show.aliasprefix=sh shwork
-  @  7b570 commit for book2
-  o  b757f commit for book1
-  o  ba592 initial
+  @  7b57 commit for book2
+  o  b757 commit for book1
+  o  ba59 initial
 
   $ hg --config commands.show.aliasprefix='s sh' swork
-  @  7b570 commit for book2
-  o  b757f commit for book1
-  o  ba592 initial
+  @  7b57 commit for book2
+  o  b757 commit for book1
+  o  ba59 initial
 
   $ hg --config commands.show.aliasprefix='s sh' shwork
-  @  7b570 commit for book2
-  o  b757f commit for book1
-  o  ba592 initial
+  @  7b57 commit for book2
+  o  b757 commit for book1
+  o  ba59 initial
 
 The aliases don't appear in `hg config`
 
   $ hg --config commands.show.aliasprefix=s config alias
   [1]
 
 Doesn't overwrite existing alias
 
   $ hg --config alias.swork='log -r .' --config commands.show.aliasprefix=s swork
   changeset:   2:7b5709ab64cb
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     commit for book2
   
 
   $ hg --config alias.swork='log -r .' --config commands.show.aliasprefix=s config alias
   alias.swork=log -r .
 
   $ cd ..