diff -r 8836f13e3c5b -r a31634336471 tests/drawdag.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/drawdag.py	Wed Nov 09 16:01:34 2016 +0000
@@ -0,0 +1,311 @@
+# drawdag.py - convert ASCII revision DAG to actual changesets
+#
+# Copyright 2016 Facebook, Inc.
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+"""
+create changesets from an ASCII graph for testing purpose.
+
+For example, given the following input::
+
+    c d
+    |/
+    b
+    |
+    a
+
+4 changesets and 4 local tags will be created.
+`hg log -G -T "{rev} {desc} (tag: {tags})"` will output::
+
+    o  3 d (tag: d tip)
+    |
+    | o  2 c (tag: c)
+    |/
+    o  1 b (tag: b)
+    |
+    o  0 a (tag: a)
+
+For root nodes (nodes without parents) in the graph, they can be revsets
+pointing to existing nodes.  The ASCII graph could also have disconnected
+components with same names referring to the same changeset.
+
+Therefore, given the repo having the 4 changesets (and tags) above, with the
+following ASCII graph as input::
+
+    foo    bar       bar  foo
+     |     /          |    |
+    ancestor(c,d)     a   baz
+
+The result (`hg log -G -T "{desc}"`) will look like::
+
+    o    foo
+    |\
+    +---o  bar
+    | | |
+    | o |  baz
+    |  /
+    +---o  d
+    | |
+    +---o  c
+    | |
+    o |  b
+    |/
+    o  a
+
+Note that if you take the above `hg log` output directly as input. It will work
+as expected - the result would be an isomorphic graph::
+
+    o    foo
+    |\
+    | | o  d
+    | |/
+    | | o  c
+    | |/
+    | | o  bar
+    | |/|
+    | o |  b
+    | |/
+    o /  baz
+     /
+    o  a
+
+This is because 'o' is specially handled in the input: instead of using 'o' as
+the node name, the word to the right will be used.
+"""
+from __future__ import absolute_import, print_function
+
+import collections
+import itertools
+
+from mercurial.i18n import _
+from mercurial import (
+    cmdutil,
+    context,
+    error,
+    node,
+    scmutil,
+)
+
+cmdtable = {}
+command = cmdutil.command(cmdtable)
+
+_pipechars = '\\/+-|'
+_nonpipechars = ''.join(chr(i) for i in xrange(33, 127)
+                        if chr(i) not in _pipechars)
+
+def _isname(ch):
+    """char -> bool. return True if ch looks like part of a name, False
+    otherwise"""
+    return ch in _nonpipechars
+
+def _parseasciigraph(text):
+    """str -> {str : [str]}. convert the ASCII graph to edges"""
+    lines = text.splitlines()
+    edges = collections.defaultdict(list)  # {node: []}
+
+    def get(y, x):
+        """(int, int) -> char. give a coordinate, return the char. return a
+        space for anything out of range"""
+        if x < 0 or y < 0:
+            return ' '
+        try:
+            return lines[y][x]
+        except IndexError:
+            return ' '
+
+    def getname(y, x):
+        """(int, int) -> str. like get(y, x) but concatenate left and right
+        parts. if name is an 'o', try to replace it to the right"""
+        result = ''
+        for i in itertools.count(0):
+            ch = get(y, x - i)
+            if not _isname(ch):
+                break
+            result = ch + result
+        for i in itertools.count(1):
+            ch = get(y, x + i)
+            if not _isname(ch):
+                break
+            result += ch
+        if result == 'o':
+            # special handling, find the name to the right
+            result = ''
+            for i in itertools.count(2):
+                ch = get(y, x + i)
+                if ch == ' ' or ch in _pipechars:
+                    if result or x + i >= len(lines[y]):
+                        break
+                else:
+                    result += ch
+            return result or 'o'
+        return result
+
+    def parents(y, x):
+        """(int, int) -> [str]. follow the ASCII edges at given position,
+        return a list of parents"""
+        visited = set([(y, x)])
+        visit = []
+        result = []
+
+        def follow(y, x, expected):
+            """conditionally append (y, x) to visit array, if it's a char
+            in excepted. 'o' in expected means an '_isname' test.
+            if '-' (or '+') is not in excepted, and get(y, x) is '-' (or '+'),
+            the next line (y + 1, x) will be checked instead."""
+            ch = get(y, x)
+            if any(ch == c and c not in expected for c in '-+'):
+                y += 1
+                return follow(y + 1, x, expected)
+            if ch in expected or ('o' in expected and _isname(ch)):
+                visit.append((y, x))
+
+        #  -o-  # starting point:
+        #  /|\ # follow '-' (horizontally), and '/|\' (to the bottom)
+        follow(y + 1, x, '|')
+        follow(y + 1, x - 1, '/')
+        follow(y + 1, x + 1, '\\')
+        follow(y, x - 1, '-')
+        follow(y, x + 1, '-')
+
+        while visit:
+            y, x = visit.pop()
+            if (y, x) in visited:
+                continue
+            visited.add((y, x))
+            ch = get(y, x)
+            if _isname(ch):
+                result.append(getname(y, x))
+                continue
+            elif ch == '|':
+                follow(y + 1, x, '/|o')
+                follow(y + 1, x - 1, '/')
+                follow(y + 1, x + 1, '\\')
+            elif ch == '+':
+                follow(y, x - 1, '-')
+                follow(y, x + 1, '-')
+                follow(y + 1, x - 1, '/')
+                follow(y + 1, x + 1, '\\')
+                follow(y + 1, x, '|')
+            elif ch == '\\':
+                follow(y + 1, x + 1, '\\|o')
+            elif ch == '/':
+                follow(y + 1, x - 1, '/|o')
+            elif ch == '-':
+                follow(y, x - 1, '-+o')
+                follow(y, x + 1, '-+o')
+        return result
+
+    for y, line in enumerate(lines):
+        for x, ch in enumerate(line):
+            if ch == '#':  # comment
+                break
+            if _isname(ch):
+                edges[getname(y, x)] += parents(y, x)
+
+    return dict(edges)
+
+class simplefilectx(object):
+    def __init__(self, path, data):
+        self._data = data
+        self._path = path
+
+    def data(self):
+        return self._data
+
+    def path(self):
+        return self._path
+
+    def renamed(self):
+        return None
+
+    def flags(self):
+        return ''
+
+class simplecommitctx(context.committablectx):
+    def __init__(self, repo, name, parentctxs, added=None):
+        opts = {
+            'changes': scmutil.status([], added or [], [], [], [], [], []),
+            'date': '0 0',
+            'extra': {'branch': 'default'},
+        }
+        super(simplecommitctx, self).__init__(self, name, **opts)
+        self._repo = repo
+        self._name = name
+        self._parents = parentctxs
+        self._parents.sort(key=lambda c: c.node())
+        while len(self._parents) < 2:
+            self._parents.append(repo[node.nullid])
+
+    def filectx(self, key):
+        return simplefilectx(key, self._name)
+
+    def commit(self):
+        return self._repo.commitctx(self)
+
+def _walkgraph(edges):
+    """yield node, parents in topologically order"""
+    visible = set(edges.keys())
+    remaining = {}  # {str: [str]}
+    for k, vs in edges.iteritems():
+        for v in vs:
+            if v not in remaining:
+                remaining[v] = []
+        remaining[k] = vs[:]
+    while remaining:
+        leafs = [k for k, v in remaining.items() if not v]
+        if not leafs:
+            raise error.Abort(_('the graph has cycles'))
+        for leaf in sorted(leafs):
+            if leaf in visible:
+                yield leaf, edges[leaf]
+            del remaining[leaf]
+            for k, v in remaining.iteritems():
+                if leaf in v:
+                    v.remove(leaf)
+
+@command('debugdrawdag', [])
+def debugdrawdag(ui, repo, **opts):
+    """read an ASCII graph from stdin and create changesets
+
+    The ASCII graph is like what :hg:`log -G` outputs, with each `o` replaced
+    to the name of the node. The command will create dummy changesets and local
+    tags with those names to make the dummy changesets easier to be referred
+    to.
+
+    If the name of a node is a single character 'o', It will be replaced by the
+    word to the right. This makes it easier to reuse
+    :hg:`log -G -T '{desc}'` outputs.
+
+    For root (no parents) nodes, revset can be used to query existing repo.
+    Note that the revset cannot have confusing characters which can be seen as
+    the part of the graph edges, like `|/+-\`.
+    """
+    text = ui.fin.read()
+
+    # parse the graph and make sure len(parents) <= 2 for each node
+    edges = _parseasciigraph(text)
+    for k, v in edges.iteritems():
+        if len(v) > 2:
+            raise error.Abort(_('%s: too many parents: %s')
+                              % (k, ' '.join(v)))
+
+    committed = {None: node.nullid}  # {name: node}
+
+    # for leaf nodes, try to find existing nodes in repo
+    for name, parents in edges.iteritems():
+        if len(parents) == 0:
+            try:
+                committed[name] = scmutil.revsingle(repo, name)
+            except error.RepoLookupError:
+                pass
+
+    # commit in topological order
+    for name, parents in _walkgraph(edges):
+        if name in committed:
+            continue
+        pctxs = [repo[committed[n]] for n in parents]
+        ctx = simplecommitctx(repo, name, pctxs, [name])
+        n = ctx.commit()
+        committed[name] = n
+        repo.tag(name, n, message=None, user=None, date=None, local=True)