view mercurial/store.py @ 31765:264baeef3588

show: new extension for displaying various repository data

Currently, Mercurial has a number of commands to show information. And,
there are features coming down the pipe that will introduce more
commands for showing information.

Currently, when introducing a new class of data or a view that we
wish to expose to the user, the strategy is to introduce a new command
or overload an existing command, sometimes both. For example, there is
a desire to formalize the wip/smartlog/underway/mine functionality that
many have devised. There is also a desire to introduce a "topics"
concept. Others would like views of "the current stack." In the
current model, we'd need a new command for wip/smartlog/etc (that
behaves a lot like a pre-defined alias of `hg log`). For topics,
we'd likely overload `hg topic[s]` to both display and manipulate
topics.

Adding new commands for every pre-defined query doesn't scale well
and pollutes `hg help`. Overloading commands to perform read-only and
write operations is arguably an UX anti-pattern: while having all
functionality for a given concept in one command is nice, having a
single command doing multiple discrete operations is not. Furthermore,
a user may be surprised that a command they thought was read-only
actually changes something.

We discussed this at the Mercurial 4.0 Sprint in Paris and decided that
having a single command where we could hang pre-defined views of
various data would be a good idea. Having such a command would:

* Help prevent an explosion of new query-related commands
* Create a clear separation between read and write operations
  (mitigates footguns)
* Avoids overloading the meaning of commands that manipulate data
  (bookmark, tag, branch, etc) (while we can't take away the
  existing behavior for BC reasons, we now won't introduce this
  behavior on new commands)
* Allows users to discover informational views more easily by
  aggregating them in a single location
* Lowers the barrier to creating the new views (since the barrier
  to creating a top-level command is relatively high)

So, this commit introduces the `hg show` command via the "show"
extension. This command accepts a positional argument of the
"view" to show. New views can be registered with a decorator. To
prove it works, we implement the "bookmarks" view, which shows a
table of bookmarks and their associated nodes.

We introduce a new style to hold everything used by `hg show`.

For our initial bookmarks view, the output varies from `hg bookmarks`:

* Padding is performed in the template itself as opposed to Python
* Revision integers are not shown
* shortest() is used to display a 5 character node by default (as
  opposed to static 12 characters)

I chose to implement the "bookmarks" view first because it is simple
and shouldn't invite too much bikeshedding that detracts from the
evaluation of `hg show` itself. But there is an important point
to consider: we now have 2 ways to show a list of bookmarks. I'm not
a fan of introducing multiple ways to do very similar things. So it
might be worth discussing how we wish to tackle this issue for
bookmarks, tags, branches, MQ series, etc.

I also made the choice of explicitly declaring the default show
template not part of the standard BC guarantees. History has shown
that we make mistakes and poor choices with output formatting but
can't fix these mistakes later because random tools are parsing
output and we don't want to break these tools. Optimizing for human
consumption is one of my goals for `hg show`. So, by not covering
the formatting as part of BC, the barrier to future change is much
lower and humans benefit.

There are some improvements that can be made to formatting. For
example, we don't yet use label() in the templates. We obviously
want this for color. But I'm not sure if we should reuse the existing
log.* labels or invent new ones. I figure we can punt that to a
follow-up.

At the aforementioned Sprint, we discussed and discarded various
alternatives to `hg show`.

We considered making `hg log <view>` perform this behavior. The main
reason we can't do this is because a positional argument to `hg log`
can be a file path and if there is a conflict between a path name and
a view name, behavior is ambiguous. We could have introduced
`hg log --view` or similar, but we felt that required too much typing
(we don't want to require a command flag to show a view) and wasn't
very discoverable. Furthermore, `hg log` is optimized for showing
changelog data and there are things that `hg display` could display
that aren't changelog centric.

There were concerns about using "show" as the command name.

Some users already have a "show" alias that is similar to `hg export`.

There were also concerns that Git users adapted to `git show` would
be confused by `hg show`'s different behavior. The main difference
here is `git show` prints an `hg export` like view of the current
commit by default and `hg show` requires an argument. `git show`
can also display any Git object. `git show` does not support
displaying more complex views: just single objects. If we
implemented `hg show <hash>` or `hg show <identifier>`, `hg show`
would be a superset of `git show`. Although, I'm hesitant to do that
at this time because I view `hg show` as a higher-level querying
command and there are namespace collisions between valid identifiers
and registered views.

There is also a prefix collision with `hg showconfig`, which is an
alias of `hg config`.

We also considered `hg view`, but that is already used by the "hgk"
extension.

`hg display` was also proposed at one point. It has a prefix collision
with `hg diff`. General consensus was "show" or "view" are the best
verbs. And since "view" was taken, "show" was chosen.

There are a number of inline TODOs in this patch. Some of these
represent decisions yet to be made. Others represent features
requiring non-trivial complexity. Rather than bloat the patch or
invite additional bikeshedding, I figured I'd document future
enhancements via TODO so we can get a minimal implmentation landed.
Something is better than nothing.

# store.py - repository store handling for Mercurial
#
# Copyright 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 __future__ import absolute_import

import errno
import hashlib
import os
import stat

from .i18n import _
from . import (
    error,
    parsers,
    pycompat,
    util,
    vfs as vfsmod,
)

# This avoids a collision between a file named foo and a dir named
# foo.i or foo.d
def _encodedir(path):
    '''
    >>> _encodedir('data/foo.i')
    'data/foo.i'
    >>> _encodedir('data/foo.i/bla.i')
    'data/foo.i.hg/bla.i'
    >>> _encodedir('data/foo.i.hg/bla.i')
    'data/foo.i.hg.hg/bla.i'
    >>> _encodedir('data/foo.i\\ndata/foo.i/bla.i\\ndata/foo.i.hg/bla.i\\n')
    'data/foo.i\\ndata/foo.i.hg/bla.i\\ndata/foo.i.hg.hg/bla.i\\n'
    '''
    return (path
            .replace(".hg/", ".hg.hg/")
            .replace(".i/", ".i.hg/")
            .replace(".d/", ".d.hg/"))

encodedir = getattr(parsers, 'encodedir', _encodedir)

def decodedir(path):
    '''
    >>> decodedir('data/foo.i')
    'data/foo.i'
    >>> decodedir('data/foo.i.hg/bla.i')
    'data/foo.i/bla.i'
    >>> decodedir('data/foo.i.hg.hg/bla.i')
    'data/foo.i.hg/bla.i'
    '''
    if ".hg/" not in path:
        return path
    return (path
            .replace(".d.hg/", ".d/")
            .replace(".i.hg/", ".i/")
            .replace(".hg.hg/", ".hg/"))

def _reserved():
    ''' characters that are problematic for filesystems

    * ascii escapes (0..31)
    * ascii hi (126..255)
    * windows specials

    these characters will be escaped by encodefunctions
    '''
    winreserved = [ord(x) for x in u'\\:*?"<>|']
    for x in range(32):
        yield x
    for x in range(126, 256):
        yield x
    for x in winreserved:
        yield x

def _buildencodefun():
    '''
    >>> enc, dec = _buildencodefun()

    >>> enc('nothing/special.txt')
    'nothing/special.txt'
    >>> dec('nothing/special.txt')
    'nothing/special.txt'

    >>> enc('HELLO')
    '_h_e_l_l_o'
    >>> dec('_h_e_l_l_o')
    'HELLO'

    >>> enc('hello:world?')
    'hello~3aworld~3f'
    >>> dec('hello~3aworld~3f')
    'hello:world?'

    >>> enc('the\x07quick\xADshot')
    'the~07quick~adshot'
    >>> dec('the~07quick~adshot')
    'the\\x07quick\\xadshot'
    '''
    e = '_'
    xchr = pycompat.bytechr
    asciistr = list(map(xchr, range(127)))
    capitals = list(range(ord("A"), ord("Z") + 1))

    cmap = dict((x, x) for x in asciistr)
    for x in _reserved():
        cmap[xchr(x)] = "~%02x" % x
    for x in capitals + [ord(e)]:
        cmap[xchr(x)] = e + xchr(x).lower()

    dmap = {}
    for k, v in cmap.iteritems():
        dmap[v] = k
    def decode(s):
        i = 0
        while i < len(s):
            for l in xrange(1, 4):
                try:
                    yield dmap[s[i:i + l]]
                    i += l
                    break
                except KeyError:
                    pass
            else:
                raise KeyError
    return (lambda s: ''.join([cmap[s[c:c + 1]] for c in xrange(len(s))]),
            lambda s: ''.join(list(decode(s))))

_encodefname, _decodefname = _buildencodefun()

def encodefilename(s):
    '''
    >>> encodefilename('foo.i/bar.d/bla.hg/hi:world?/HELLO')
    'foo.i.hg/bar.d.hg/bla.hg.hg/hi~3aworld~3f/_h_e_l_l_o'
    '''
    return _encodefname(encodedir(s))

def decodefilename(s):
    '''
    >>> decodefilename('foo.i.hg/bar.d.hg/bla.hg.hg/hi~3aworld~3f/_h_e_l_l_o')
    'foo.i/bar.d/bla.hg/hi:world?/HELLO'
    '''
    return decodedir(_decodefname(s))

def _buildlowerencodefun():
    '''
    >>> f = _buildlowerencodefun()
    >>> f('nothing/special.txt')
    'nothing/special.txt'
    >>> f('HELLO')
    'hello'
    >>> f('hello:world?')
    'hello~3aworld~3f'
    >>> f('the\x07quick\xADshot')
    'the~07quick~adshot'
    '''
    cmap = dict([(chr(x), chr(x)) for x in xrange(127)])
    for x in _reserved():
        cmap[chr(x)] = "~%02x" % x
    for x in range(ord("A"), ord("Z") + 1):
        cmap[chr(x)] = chr(x).lower()
    return lambda s: "".join([cmap[c] for c in s])

lowerencode = getattr(parsers, 'lowerencode', None) or _buildlowerencodefun()

# Windows reserved names: con, prn, aux, nul, com1..com9, lpt1..lpt9
_winres3 = ('aux', 'con', 'prn', 'nul') # length 3
_winres4 = ('com', 'lpt')               # length 4 (with trailing 1..9)
def _auxencode(path, dotencode):
    '''
    Encodes filenames containing names reserved by Windows or which end in
    period or space. Does not touch other single reserved characters c.
    Specifically, c in '\\:*?"<>|' or ord(c) <= 31 are *not* encoded here.
    Additionally encodes space or period at the beginning, if dotencode is
    True. Parameter path is assumed to be all lowercase.
    A segment only needs encoding if a reserved name appears as a
    basename (e.g. "aux", "aux.foo"). A directory or file named "foo.aux"
    doesn't need encoding.

    >>> s = '.foo/aux.txt/txt.aux/con/prn/nul/foo.'
    >>> _auxencode(s.split('/'), True)
    ['~2efoo', 'au~78.txt', 'txt.aux', 'co~6e', 'pr~6e', 'nu~6c', 'foo~2e']
    >>> s = '.com1com2/lpt9.lpt4.lpt1/conprn/com0/lpt0/foo.'
    >>> _auxencode(s.split('/'), False)
    ['.com1com2', 'lp~749.lpt4.lpt1', 'conprn', 'com0', 'lpt0', 'foo~2e']
    >>> _auxencode(['foo. '], True)
    ['foo.~20']
    >>> _auxencode([' .foo'], True)
    ['~20.foo']
    '''
    for i, n in enumerate(path):
        if not n:
            continue
        if dotencode and n[0] in '. ':
            n = "~%02x" % ord(n[0:1]) + n[1:]
            path[i] = n
        else:
            l = n.find('.')
            if l == -1:
                l = len(n)
            if ((l == 3 and n[:3] in _winres3) or
                (l == 4 and n[3:4] <= '9' and n[3:4] >= '1'
                        and n[:3] in _winres4)):
                # encode third letter ('aux' -> 'au~78')
                ec = "~%02x" % ord(n[2:3])
                n = n[0:2] + ec + n[3:]
                path[i] = n
        if n[-1] in '. ':
            # encode last period or space ('foo...' -> 'foo..~2e')
            path[i] = n[:-1] + "~%02x" % ord(n[-1:])
    return path

_maxstorepathlen = 120
_dirprefixlen = 8
_maxshortdirslen = 8 * (_dirprefixlen + 1) - 4

def _hashencode(path, dotencode):
    digest = hashlib.sha1(path).hexdigest()
    le = lowerencode(path[5:]).split('/') # skips prefix 'data/' or 'meta/'
    parts = _auxencode(le, dotencode)
    basename = parts[-1]
    _root, ext = os.path.splitext(basename)
    sdirs = []
    sdirslen = 0
    for p in parts[:-1]:
        d = p[:_dirprefixlen]
        if d[-1] in '. ':
            # Windows can't access dirs ending in period or space
            d = d[:-1] + '_'
        if sdirslen == 0:
            t = len(d)
        else:
            t = sdirslen + 1 + len(d)
            if t > _maxshortdirslen:
                break
        sdirs.append(d)
        sdirslen = t
    dirs = '/'.join(sdirs)
    if len(dirs) > 0:
        dirs += '/'
    res = 'dh/' + dirs + digest + ext
    spaceleft = _maxstorepathlen - len(res)
    if spaceleft > 0:
        filler = basename[:spaceleft]
        res = 'dh/' + dirs + filler + digest + ext
    return res

def _hybridencode(path, dotencode):
    '''encodes path with a length limit

    Encodes all paths that begin with 'data/', according to the following.

    Default encoding (reversible):

    Encodes all uppercase letters 'X' as '_x'. All reserved or illegal
    characters are encoded as '~xx', where xx is the two digit hex code
    of the character (see encodefilename).
    Relevant path components consisting of Windows reserved filenames are
    masked by encoding the third character ('aux' -> 'au~78', see _auxencode).

    Hashed encoding (not reversible):

    If the default-encoded path is longer than _maxstorepathlen, a
    non-reversible hybrid hashing of the path is done instead.
    This encoding uses up to _dirprefixlen characters of all directory
    levels of the lowerencoded path, but not more levels than can fit into
    _maxshortdirslen.
    Then follows the filler followed by the sha digest of the full path.
    The filler is the beginning of the basename of the lowerencoded path
    (the basename is everything after the last path separator). The filler
    is as long as possible, filling in characters from the basename until
    the encoded path has _maxstorepathlen characters (or all chars of the
    basename have been taken).
    The extension (e.g. '.i' or '.d') is preserved.

    The string 'data/' at the beginning is replaced with 'dh/', if the hashed
    encoding was used.
    '''
    path = encodedir(path)
    ef = _encodefname(path).split('/')
    res = '/'.join(_auxencode(ef, dotencode))
    if len(res) > _maxstorepathlen:
        res = _hashencode(path, dotencode)
    return res

def _pathencode(path):
    de = encodedir(path)
    if len(path) > _maxstorepathlen:
        return _hashencode(de, True)
    ef = _encodefname(de).split('/')
    res = '/'.join(_auxencode(ef, True))
    if len(res) > _maxstorepathlen:
        return _hashencode(de, True)
    return res

_pathencode = getattr(parsers, 'pathencode', _pathencode)

def _plainhybridencode(f):
    return _hybridencode(f, False)

def _calcmode(vfs):
    try:
        # files in .hg/ will be created using this mode
        mode = vfs.stat().st_mode
            # avoid some useless chmods
        if (0o777 & ~util.umask) == (0o777 & mode):
            mode = None
    except OSError:
        mode = None
    return mode

_data = ('data meta 00manifest.d 00manifest.i 00changelog.d 00changelog.i'
         ' phaseroots obsstore')

class basicstore(object):
    '''base class for local repository stores'''
    def __init__(self, path, vfstype):
        vfs = vfstype(path)
        self.path = vfs.base
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        self.vfs = vfsmod.filtervfs(vfs, encodedir)
        self.opener = self.vfs

    def join(self, f):
        return self.path + '/' + encodedir(f)

    def _walk(self, relpath, recurse):
        '''yields (unencoded, encoded, size)'''
        path = self.path
        if relpath:
            path += '/' + relpath
        striplen = len(self.path) + 1
        l = []
        if self.rawvfs.isdir(path):
            visit = [path]
            readdir = self.rawvfs.readdir
            while visit:
                p = visit.pop()
                for f, kind, st in readdir(p, stat=True):
                    fp = p + '/' + f
                    if kind == stat.S_IFREG and f[-2:] in ('.d', '.i'):
                        n = util.pconvert(fp[striplen:])
                        l.append((decodedir(n), n, st.st_size))
                    elif kind == stat.S_IFDIR and recurse:
                        visit.append(fp)
        l.sort()
        return l

    def datafiles(self):
        return self._walk('data', True) + self._walk('meta', True)

    def topfiles(self):
        # yield manifest before changelog
        return reversed(self._walk('', False))

    def walk(self):
        '''yields (unencoded, encoded, size)'''
        # yield data files first
        for x in self.datafiles():
            yield x
        for x in self.topfiles():
            yield x

    def copylist(self):
        return ['requires'] + _data.split()

    def write(self, tr):
        pass

    def invalidatecaches(self):
        pass

    def markremoved(self, fn):
        pass

    def __contains__(self, path):
        '''Checks if the store contains path'''
        path = "/".join(("data", path))
        # file?
        if self.vfs.exists(path + ".i"):
            return True
        # dir?
        if not path.endswith("/"):
            path = path + "/"
        return self.vfs.exists(path)

class encodedstore(basicstore):
    def __init__(self, path, vfstype):
        vfs = vfstype(path + '/store')
        self.path = vfs.base
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        self.vfs = vfsmod.filtervfs(vfs, encodefilename)
        self.opener = self.vfs

    def datafiles(self):
        for a, b, size in super(encodedstore, self).datafiles():
            try:
                a = decodefilename(a)
            except KeyError:
                a = None
            yield a, b, size

    def join(self, f):
        return self.path + '/' + encodefilename(f)

    def copylist(self):
        return (['requires', '00changelog.i'] +
                ['store/' + f for f in _data.split()])

class fncache(object):
    # the filename used to be partially encoded
    # hence the encodedir/decodedir dance
    def __init__(self, vfs):
        self.vfs = vfs
        self.entries = None
        self._dirty = False

    def _load(self):
        '''fill the entries from the fncache file'''
        self._dirty = False
        try:
            fp = self.vfs('fncache', mode='rb')
        except IOError:
            # skip nonexistent file
            self.entries = set()
            return
        self.entries = set(decodedir(fp.read()).splitlines())
        if '' in self.entries:
            fp.seek(0)
            for n, line in enumerate(util.iterfile(fp)):
                if not line.rstrip('\n'):
                    t = _('invalid entry in fncache, line %d') % (n + 1)
                    raise error.Abort(t)
        fp.close()

    def write(self, tr):
        if self._dirty:
            tr.addbackup('fncache')
            fp = self.vfs('fncache', mode='wb', atomictemp=True)
            if self.entries:
                fp.write(encodedir('\n'.join(self.entries) + '\n'))
            fp.close()
            self._dirty = False

    def add(self, fn):
        if self.entries is None:
            self._load()
        if fn not in self.entries:
            self._dirty = True
            self.entries.add(fn)

    def remove(self, fn):
        if self.entries is None:
            self._load()
        try:
            self.entries.remove(fn)
            self._dirty = True
        except KeyError:
            pass

    def __contains__(self, fn):
        if self.entries is None:
            self._load()
        return fn in self.entries

    def __iter__(self):
        if self.entries is None:
            self._load()
        return iter(self.entries)

class _fncachevfs(vfsmod.abstractvfs, vfsmod.auditvfs):
    def __init__(self, vfs, fnc, encode):
        vfsmod.auditvfs.__init__(self, vfs)
        self.fncache = fnc
        self.encode = encode

    def __call__(self, path, mode='r', *args, **kw):
        if mode not in ('r', 'rb') and (path.startswith('data/') or
                                        path.startswith('meta/')):
            self.fncache.add(path)
        return self.vfs(self.encode(path), mode, *args, **kw)

    def join(self, path):
        if path:
            return self.vfs.join(self.encode(path))
        else:
            return self.vfs.join(path)

class fncachestore(basicstore):
    def __init__(self, path, vfstype, dotencode):
        if dotencode:
            encode = _pathencode
        else:
            encode = _plainhybridencode
        self.encode = encode
        vfs = vfstype(path + '/store')
        self.path = vfs.base
        self.pathsep = self.path + '/'
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        fnc = fncache(vfs)
        self.fncache = fnc
        self.vfs = _fncachevfs(vfs, fnc, encode)
        self.opener = self.vfs

    def join(self, f):
        return self.pathsep + self.encode(f)

    def getsize(self, path):
        return self.rawvfs.stat(path).st_size

    def datafiles(self):
        for f in sorted(self.fncache):
            ef = self.encode(f)
            try:
                yield f, ef, self.getsize(ef)
            except OSError as err:
                if err.errno != errno.ENOENT:
                    raise

    def copylist(self):
        d = ('data meta dh fncache phaseroots obsstore'
             ' 00manifest.d 00manifest.i 00changelog.d 00changelog.i')
        return (['requires', '00changelog.i'] +
                ['store/' + f for f in d.split()])

    def write(self, tr):
        self.fncache.write(tr)

    def invalidatecaches(self):
        self.fncache.entries = None

    def markremoved(self, fn):
        self.fncache.remove(fn)

    def _exists(self, f):
        ef = self.encode(f)
        try:
            self.getsize(ef)
            return True
        except OSError as err:
            if err.errno != errno.ENOENT:
                raise
            # nonexistent entry
            return False

    def __contains__(self, path):
        '''Checks if the store contains path'''
        path = "/".join(("data", path))
        # check for files (exact match)
        e = path + '.i'
        if e in self.fncache and self._exists(e):
            return True
        # now check for directories (prefix match)
        if not path.endswith('/'):
            path += '/'
        for e in self.fncache:
            if e.startswith(path) and self._exists(e):
                return True
        return False

def store(requirements, path, vfstype):
    if 'store' in requirements:
        if 'fncache' in requirements:
            return fncachestore(path, vfstype, 'dotencode' in requirements)
        return encodedstore(path, vfstype)
    return basicstore(path, vfstype)