mercurial/filemerge.py

filemerge: add internal:tagmerge merge tool

Add a new internal:tagmerge merge tool which implements an automatic merge
algorithm for mercurial's tag files

The tagmerge algorithm is able to resolve most merge conflicts that
currently would trigger a .hgtags merge conflict. The only case that
it does not (and cannot) handle is that in which two tags point to
different revisions on each merge parent _and_ their corresponding tag
histories have the same rank (i.e. the same length). In all other
cases the merge algorithm will choose the revision belonging to the
parent with the highest ranked tag history. The merged tag history is
the combination of both tag histories (special care is taken to try to
combine common tag histories where possible).

The algorithm also handles cases in which tags have been manually
removed from the .hgtags file and other similar corner cases.

In addition to actually merging the tags from two parents, taking into
account the base, the algorithm also tries to minimize the difference
between the merged tag file and the first parent's tag file (i.e. it
tries to make the merged tag order as as similar as possible to the
first parent's tag file order).

The algorithm works as follows:
1. read the tags from p1, p2 and the base
    - when reading the p1 tags, also get the line numbers associated to each
      tag node (these will be used to sort the merged tags in a way that
      minimizes the diff to p1). Ignore the file numbers when reading p2 and
      the base
2. recover the "lost tags" (i.e. those that are found in the base but not on p1
   or p2) and add them back to p1 and/or p2
    - at this point the only tags that are on p1 but not on p2 are those new
      tags that were introduced in p1. Same thing for the tags that are on p2
      but not on p2
3. take all tags that are only on p1 or only on p2 (but not on the base)
    - Note that these are the tags that were introduced between base and p1 and
      between base and p2, possibly on separate clones
4. for each tag found both on p1 and p2 perform the following merge algorithm:
    - the tags conflict if their tag "histories" have the same "rank" (i.e.
      length) _AND_ the last (current) tag is _NOT_ the same
    - for non conflicting tags:
        - choose which are the high and the low ranking nodes
            - the high ranking list of nodes is the one that is longer.
              In case of draw favor p1
            - the merged node list is made of 3 parts:
                - first the nodes that are common to the beginning of both the
                  low and the high ranking nodes
                - second the non common low ranking nodes
                - finally the non common high ranking nodes (with the last one
                  being the merged tag node)
            - note that this is equivalent to putting the whole low ranking node
              list first, followed by the non common high ranking nodes
    - note that during the merge we keep the "node line numbers", which will
      be used when writing the merged tags to the tag file
5. write the merged tags taking into account to their positions in the first
   parent (i.e. try to keep the relative ordering of the nodes that come
   from p1). This minimizes the diff between the merged and the p1 tag files
   This is done by using the following algorithm
    - group the nodes for a given tag that must be written next to each other
        - A: nodes that come from consecutive lines on p1
        - B: nodes that come from p2 (i.e. whose associated line number is None)
             and are next to one of the a nodes in A
        - each group is associated with a line number coming from p1
    - generate a "tag block" for each of the groups
        - a tag block is a set of consecutive "node tag" lines belonging to the
          same tag and which will be written next to each other on the merged
          tags file
    - sort the "tag blocks" according to their associated number line
        - put blocks whose nodes come all from p2 first
    - write the tag blocks in the sorted order

Notes:
- A few tests have been added to test-tag.t. These tests are very specific to
the new internal:tagmerge tool, so perhaps they should be moved to their own
test file.
- The merge algorithm was discussed in a thread on the mercurial mailing list.
In http://markmail.org/message/anqaxldup4tmgyrx a slightly different algorithm
was suggested. In it the p1 and p2 tags would have been interleaved instead of
put one before the other. It would be possible to implement that but my tests
suggest that the merge result would be more confusing and harder to understand.

# filemerge.py - file-level merge handling for Mercurial
#
# Copyright 2006, 2007, 2008 Matt Mackall <[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.

from node import short
from i18n import _
import util, simplemerge, match, error, templater, templatekw
import os, tempfile, re, filecmp
import tagmerge

def _toolstr(ui, tool, part, default=""):
    return ui.config("merge-tools", tool + "." + part, default)

def _toolbool(ui, tool, part, default=False):
    return ui.configbool("merge-tools", tool + "." + part, default)

def _toollist(ui, tool, part, default=[]):
    return ui.configlist("merge-tools", tool + "." + part, default)

internals = {}

def internaltool(name, trymerge, onfailure=None):
    '''return a decorator for populating internal merge tool table'''
    def decorator(func):
        fullname = 'internal:' + name
        func.__doc__ = "``%s``\n" % fullname + func.__doc__.strip()
        internals[fullname] = func
        func.trymerge = trymerge
        func.onfailure = onfailure
        return func
    return decorator

def _findtool(ui, tool):
    if tool in internals:
        return tool
    for kn in ("regkey", "regkeyalt"):
        k = _toolstr(ui, tool, kn)
        if not k:
            continue
        p = util.lookupreg(k, _toolstr(ui, tool, "regname"))
        if p:
            p = util.findexe(p + _toolstr(ui, tool, "regappend"))
            if p:
                return p
    exe = _toolstr(ui, tool, "executable", tool)
    return util.findexe(util.expandpath(exe))

def _picktool(repo, ui, path, binary, symlink):
    def check(tool, pat, symlink, binary):
        tmsg = tool
        if pat:
            tmsg += " specified for " + pat
        if not _findtool(ui, tool):
            if pat: # explicitly requested tool deserves a warning
                ui.warn(_("couldn't find merge tool %s\n") % tmsg)
            else: # configured but non-existing tools are more silent
                ui.note(_("couldn't find merge tool %s\n") % tmsg)
        elif symlink and not _toolbool(ui, tool, "symlink"):
            ui.warn(_("tool %s can't handle symlinks\n") % tmsg)
        elif binary and not _toolbool(ui, tool, "binary"):
            ui.warn(_("tool %s can't handle binary\n") % tmsg)
        elif not util.gui() and _toolbool(ui, tool, "gui"):
            ui.warn(_("tool %s requires a GUI\n") % tmsg)
        else:
            return True
        return False

    # forcemerge comes from command line arguments, highest priority
    force = ui.config('ui', 'forcemerge')
    if force:
        toolpath = _findtool(ui, force)
        if toolpath:
            return (force, util.shellquote(toolpath))
        else:
            # mimic HGMERGE if given tool not found
            return (force, force)

    # HGMERGE takes next precedence
    hgmerge = os.environ.get("HGMERGE")
    if hgmerge:
        return (hgmerge, hgmerge)

    # then patterns
    for pat, tool in ui.configitems("merge-patterns"):
        mf = match.match(repo.root, '', [pat])
        if mf(path) and check(tool, pat, symlink, False):
            toolpath = _findtool(ui, tool)
            return (tool, util.shellquote(toolpath))

    # then merge tools
    tools = {}
    for k, v in ui.configitems("merge-tools"):
        t = k.split('.')[0]
        if t not in tools:
            tools[t] = int(_toolstr(ui, t, "priority", "0"))
    names = tools.keys()
    tools = sorted([(-p, t) for t, p in tools.items()])
    uimerge = ui.config("ui", "merge")
    if uimerge:
        if uimerge not in names:
            return (uimerge, uimerge)
        tools.insert(0, (None, uimerge)) # highest priority
    tools.append((None, "hgmerge")) # the old default, if found
    for p, t in tools:
        if check(t, None, symlink, binary):
            toolpath = _findtool(ui, t)
            return (t, util.shellquote(toolpath))

    # internal merge or prompt as last resort
    if symlink or binary:
        return "internal:prompt", None
    return "internal:merge", None

def _eoltype(data):
    "Guess the EOL type of a file"
    if '\0' in data: # binary
        return None
    if '\r\n' in data: # Windows
        return '\r\n'
    if '\r' in data: # Old Mac
        return '\r'
    if '\n' in data: # UNIX
        return '\n'
    return None # unknown

def _matcheol(file, origfile):
    "Convert EOL markers in a file to match origfile"
    tostyle = _eoltype(util.readfile(origfile))
    if tostyle:
        data = util.readfile(file)
        style = _eoltype(data)
        if style:
            newdata = data.replace(style, tostyle)
            if newdata != data:
                util.writefile(file, newdata)

@internaltool('prompt', False)
def _iprompt(repo, mynode, orig, fcd, fco, fca, toolconf):
    """Asks the user which of the local or the other version to keep as
    the merged version."""
    ui = repo.ui
    fd = fcd.path()

    if ui.promptchoice(_(" no tool found to merge %s\n"
                         "keep (l)ocal or take (o)ther?"
                         "$$ &Local $$ &Other") % fd, 0):
        return _iother(repo, mynode, orig, fcd, fco, fca, toolconf)
    else:
        return _ilocal(repo, mynode, orig, fcd, fco, fca, toolconf)

@internaltool('local', False)
def _ilocal(repo, mynode, orig, fcd, fco, fca, toolconf):
    """Uses the local version of files as the merged version."""
    return 0

@internaltool('other', False)
def _iother(repo, mynode, orig, fcd, fco, fca, toolconf):
    """Uses the other version of files as the merged version."""
    repo.wwrite(fcd.path(), fco.data(), fco.flags())
    return 0

@internaltool('fail', False)
def _ifail(repo, mynode, orig, fcd, fco, fca, toolconf):
    """
    Rather than attempting to merge files that were modified on both
    branches, it marks them as unresolved. The resolve command must be
    used to resolve these conflicts."""
    return 1

def _premerge(repo, toolconf, files, labels=None):
    tool, toolpath, binary, symlink = toolconf
    if symlink:
        return 1
    a, b, c, back = files

    ui = repo.ui

    # do we attempt to simplemerge first?
    try:
        premerge = _toolbool(ui, tool, "premerge", not binary)
    except error.ConfigError:
        premerge = _toolstr(ui, tool, "premerge").lower()
        valid = 'keep'.split()
        if premerge not in valid:
            _valid = ', '.join(["'" + v + "'" for v in valid])
            raise error.ConfigError(_("%s.premerge not valid "
                                      "('%s' is neither boolean nor %s)") %
                                    (tool, premerge, _valid))

    if premerge:
        r = simplemerge.simplemerge(ui, a, b, c, quiet=True, label=labels)
        if not r:
            ui.debug(" premerge successful\n")
            return 0
        if premerge != 'keep':
            util.copyfile(back, a) # restore from backup and try again
    return 1 # continue merging

@internaltool('merge', True,
              _("merging %s incomplete! "
                "(edit conflicts, then use 'hg resolve --mark')\n"))
def _imerge(repo, mynode, orig, fcd, fco, fca, toolconf, files, labels=None):
    """
    Uses the internal non-interactive simple merge algorithm for merging
    files. It will fail if there are any conflicts and leave markers in
    the partially merged file."""
    tool, toolpath, binary, symlink = toolconf
    if symlink:
        repo.ui.warn(_('warning: internal:merge cannot merge symlinks '
                       'for %s\n') % fcd.path())
        return False, 1
    r = _premerge(repo, toolconf, files, labels=labels)
    if r:
        a, b, c, back = files

        ui = repo.ui

        r = simplemerge.simplemerge(ui, a, b, c, label=labels, no_minimal=True)
        return True, r
    return False, 0

@internaltool('tagmerge', True,
              _("automatic tag merging of %s failed! "
                "(use 'hg resolve --tool internal:merge' or another merge "
                "tool of your choice)\n"))
def _itagmerge(repo, mynode, orig, fcd, fco, fca, toolconf, files, labels=None):
    """
    Uses the internal tag merge algorithm (experimental).
    """
    return tagmerge.merge(repo, fcd, fco, fca)

@internaltool('dump', True)
def _idump(repo, mynode, orig, fcd, fco, fca, toolconf, files, labels=None):
    """
    Creates three versions of the files to merge, containing the
    contents of local, other and base. These files can then be used to
    perform a merge manually. If the file to be merged is named
    ``a.txt``, these files will accordingly be named ``a.txt.local``,
    ``a.txt.other`` and ``a.txt.base`` and they will be placed in the
    same directory as ``a.txt``."""
    r = _premerge(repo, toolconf, files, labels=labels)
    if r:
        a, b, c, back = files

        fd = fcd.path()

        util.copyfile(a, a + ".local")
        repo.wwrite(fd + ".other", fco.data(), fco.flags())
        repo.wwrite(fd + ".base", fca.data(), fca.flags())
    return False, r

def _xmerge(repo, mynode, orig, fcd, fco, fca, toolconf, files, labels=None):
    r = _premerge(repo, toolconf, files, labels=labels)
    if r:
        tool, toolpath, binary, symlink = toolconf
        a, b, c, back = files
        out = ""
        env = {'HG_FILE': fcd.path(),
               'HG_MY_NODE': short(mynode),
               'HG_OTHER_NODE': str(fco.changectx()),
               'HG_BASE_NODE': str(fca.changectx()),
               'HG_MY_ISLINK': 'l' in fcd.flags(),
               'HG_OTHER_ISLINK': 'l' in fco.flags(),
               'HG_BASE_ISLINK': 'l' in fca.flags(),
               }

        ui = repo.ui

        args = _toolstr(ui, tool, "args", '$local $base $other')
        if "$output" in args:
            out, a = a, back # read input from backup, write to original
        replace = {'local': a, 'base': b, 'other': c, 'output': out}
        args = util.interpolate(r'\$', replace, args,
                                lambda s: util.shellquote(util.localpath(s)))
        r = util.system(toolpath + ' ' + args, cwd=repo.root, environ=env,
                        out=ui.fout)
        return True, r
    return False, 0

def _formatconflictmarker(repo, ctx, template, label, pad):
    """Applies the given template to the ctx, prefixed by the label.

    Pad is the minimum width of the label prefix, so that multiple markers
    can have aligned templated parts.
    """
    if ctx.node() is None:
        ctx = ctx.p1()

    props = templatekw.keywords.copy()
    props['templ'] = template
    props['ctx'] = ctx
    props['repo'] = repo
    templateresult = template('conflictmarker', **props)

    label = ('%s:' % label).ljust(pad + 1)
    mark = '%s %s' % (label, templater.stringify(templateresult))

    if mark:
        mark = mark.splitlines()[0] # split for safety

    # 8 for the prefix of conflict marker lines (e.g. '<<<<<<< ')
    return util.ellipsis(mark, 80 - 8)

_defaultconflictmarker = ('{node|short} ' +
    '{ifeq(tags, "tip", "", "{tags} ")}' +
    '{if(bookmarks, "{bookmarks} ")}' +
    '{ifeq(branch, "default", "", "{branch} ")}' +
    '- {author|user}: {desc|firstline}')

_defaultconflictlabels = ['local', 'other']

def _formatlabels(repo, fcd, fco, labels):
    """Formats the given labels using the conflict marker template.

    Returns a list of formatted labels.
    """
    cd = fcd.changectx()
    co = fco.changectx()

    ui = repo.ui
    template = ui.config('ui', 'mergemarkertemplate', _defaultconflictmarker)
    template = templater.parsestring(template, quoted=False)
    tmpl = templater.templater(None, cache={ 'conflictmarker' : template })

    pad = max(len(labels[0]), len(labels[1]))

    return [_formatconflictmarker(repo, cd, tmpl, labels[0], pad),
            _formatconflictmarker(repo, co, tmpl, labels[1], pad)]

def filemerge(repo, mynode, orig, fcd, fco, fca, labels=None):
    """perform a 3-way merge in the working directory

    mynode = parent node before merge
    orig = original local filename before merge
    fco = other file context
    fca = ancestor file context
    fcd = local file context for current/destination file
    """

    def temp(prefix, ctx):
        pre = "%s~%s." % (os.path.basename(ctx.path()), prefix)
        (fd, name) = tempfile.mkstemp(prefix=pre)
        data = repo.wwritedata(ctx.path(), ctx.data())
        f = os.fdopen(fd, "wb")
        f.write(data)
        f.close()
        return name

    if not fco.cmp(fcd): # files identical?
        return None

    ui = repo.ui
    fd = fcd.path()
    binary = fcd.isbinary() or fco.isbinary() or fca.isbinary()
    symlink = 'l' in fcd.flags() + fco.flags()
    tool, toolpath = _picktool(repo, ui, fd, binary, symlink)
    ui.debug("picked tool '%s' for %s (binary %s symlink %s)\n" %
               (tool, fd, binary, symlink))

    if tool in internals:
        func = internals[tool]
        trymerge = func.trymerge
        onfailure = func.onfailure
    else:
        func = _xmerge
        trymerge = True
        onfailure = _("merging %s failed!\n")

    toolconf = tool, toolpath, binary, symlink

    if not trymerge:
        return func(repo, mynode, orig, fcd, fco, fca, toolconf)

    a = repo.wjoin(fd)
    b = temp("base", fca)
    c = temp("other", fco)
    back = a + ".orig"
    util.copyfile(a, back)

    if orig != fco.path():
        ui.status(_("merging %s and %s to %s\n") % (orig, fco.path(), fd))
    else:
        ui.status(_("merging %s\n") % fd)

    ui.debug("my %s other %s ancestor %s\n" % (fcd, fco, fca))

    markerstyle = ui.config('ui', 'mergemarkers', 'basic')
    if markerstyle == 'basic':
        formattedlabels = _defaultconflictlabels
    else:
        if not labels:
            labels = _defaultconflictlabels

        formattedlabels = _formatlabels(repo, fcd, fco, labels)

    needcheck, r = func(repo, mynode, orig, fcd, fco, fca, toolconf,
                        (a, b, c, back), labels=formattedlabels)
    if not needcheck:
        if r:
            if onfailure:
                ui.warn(onfailure % fd)
        else:
            util.unlink(back)

        util.unlink(b)
        util.unlink(c)
        return r

    if not r and (_toolbool(ui, tool, "checkconflicts") or
                  'conflicts' in _toollist(ui, tool, "check")):
        if re.search("^(<<<<<<< .*|=======|>>>>>>> .*)$", fcd.data(),
                     re.MULTILINE):
            r = 1

    checked = False
    if 'prompt' in _toollist(ui, tool, "check"):
        checked = True
        if ui.promptchoice(_("was merge of '%s' successful (yn)?"
                             "$$ &Yes $$ &No") % fd, 1):
            r = 1

    if not r and not checked and (_toolbool(ui, tool, "checkchanged") or
                                  'changed' in _toollist(ui, tool, "check")):
        if filecmp.cmp(a, back):
            if ui.promptchoice(_(" output file %s appears unchanged\n"
                                 "was merge successful (yn)?"
                                 "$$ &Yes $$ &No") % fd, 1):
                r = 1

    if _toolbool(ui, tool, "fixeol"):
        _matcheol(a, back)

    if r:
        if onfailure:
            ui.warn(onfailure % fd)
    else:
        util.unlink(back)

    util.unlink(b)
    util.unlink(c)
    return r

# tell hggettext to extract docstrings from these functions:
i18nfunctions = internals.values()