mercurial/graphmod.py

dirstate: ignore symlinks when fs cannot handle them (issue1888)

When the filesystem cannot handle the executable bit, we currently
ignore it completely when looking for modified files. Similarly, it is
impossible to set or clear the bit when the filesystem ignores it.

This patch makes Mercurial treat symbolic links the same way.

Symlinks are a little different since they manifest themselves as
small files containing a filename (the symlink target). On Windows,
these files show up as regular files, and on Linux and Mac they show
up as real symlinks.

Issue1888 presents a case where the symlink files are better ignored
from the Windows side. A Linux client creates symlinks in a working
copy which is shared over a network between Linux and Windows clients.

The Samba server is helpful and defererences the symlink when the
Windows client looks at it. This means that Mercurial on the Windows
side sees file content instead of a file name in the symlink, and
hence flags the link as modified. Ignoring the change would be much
more helpful, similarly to how Mercurial does not report any changes
when executable bits are ignored in a checkout on Windows.

An initial checkout of a symbolic link on a file system that cannot
handle symbolic links will still result in a regular file containing
the target file name as its content. Sharing such a checkout with a
Linux client will not turn the file into a symlink automatically, but
'hg revert' can fix that. After the revert, the Windows client will
see the correct file content (provided by the Samba server when it
follows the link on the Linux side) and otherwise ignore the change.

Running 'hg perfstatus' 10 times gives these results:

  Before:          After:
  min: 0.544703    min: 0.546549
  med: 0.547592    med: 0.548881
  avg: 0.549146    avg: 0.548549
  max: 0.564112    max: 0.551504

The median time is increased about 0.24%.

# Revision graph generator for Mercurial
#
# Copyright 2008 Dirkjan Ochtman <[e-mail]>
# Copyright 2007 Joel Rosdahl <[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.

"""supports walking the history as DAGs suitable for graphical output

The most basic format we use is that of::

  (id, type, data, [parentids])

The node and parent ids are arbitrary integers which identify a node in the
context of the graph returned. Type is a constant specifying the node type.
Data depends on type.
"""

from mercurial.node import nullrev

CHANGESET = 'C'

def revisions(repo, start, stop):
    """cset DAG generator yielding (id, CHANGESET, ctx, [parentids]) tuples

    This generator function walks through the revision history from revision
    start to revision stop (which must be less than or equal to start). It
    returns a tuple for each node. The node and parent ids are arbitrary
    integers which identify a node in the context of the graph returned.
    """
    cur = start
    while cur >= stop:
        ctx = repo[cur]
        parents = [p.rev() for p in ctx.parents() if p.rev() != nullrev]
        yield (cur, CHANGESET, ctx, sorted(parents))
        cur -= 1

def filerevs(repo, path, start, stop, limit=None):
    """file cset DAG generator yielding (id, CHANGESET, ctx, [parentids]) tuples

    This generator function walks through the revision history of a single
    file from revision start down to revision stop.
    """
    filerev = len(repo.file(path)) - 1
    rev = stop + 1
    count = 0
    while filerev >= 0 and rev > stop:
        fctx = repo.filectx(path, fileid=filerev)
        parents = [f.linkrev() for f in fctx.parents() if f.path() == path]
        rev = fctx.rev()
        if rev <= start:
            yield (rev, CHANGESET, fctx.changectx(), sorted(parents))
            count += 1
            if count == limit:
                break
        filerev -= 1

def nodes(repo, nodes):
    """cset DAG generator yielding (id, CHANGESET, ctx, [parentids]) tuples

    This generator function walks the given nodes. It only returns parents
    that are in nodes, too.
    """
    include = set(nodes)
    for node in nodes:
        ctx = repo[node]
        parents = [p.rev() for p in ctx.parents() if p.node() in include]
        yield (ctx.rev(), CHANGESET, ctx, sorted(parents))

def colored(dag):
    """annotates a DAG with colored edge information

    For each DAG node this function emits tuples::

      (id, type, data, (col, color), [(col, nextcol, color)])

    with the following new elements:

      - Tuple (col, color) with column and color index for the current node
      - A list of tuples indicating the edges between the current node and its
        parents.
    """
    seen = []
    colors = {}
    newcolor = 1
    for (cur, type, data, parents) in dag:

        # Compute seen and next
        if cur not in seen:
            seen.append(cur) # new head
            colors[cur] = newcolor
            newcolor += 1

        col = seen.index(cur)
        color = colors.pop(cur)
        next = seen[:]

        # Add parents to next
        addparents = [p for p in parents if p not in next]
        next[col:col + 1] = addparents

        # Set colors for the parents
        for i, p in enumerate(addparents):
            if not i:
                colors[p] = color
            else:
                colors[p] = newcolor
                newcolor += 1

        # Add edges to the graph
        edges = []
        for ecol, eid in enumerate(seen):
            if eid in next:
                edges.append((ecol, next.index(eid), colors[eid]))
            elif eid == cur:
                for p in parents:
                    edges.append((ecol, next.index(p), color))

        # Yield and move on
        yield (cur, type, data, (col, color), edges)
        seen = next