mercurial/node.py

match: add `filepath:` pattern to match an exact filepath relative to the root

It's useful in certain automated workflows to make sure we recurse in
directories whose name conflicts with files in other revisions.

In addition it makes it possible to avoid building a potentially costly regex,
improving performance when the set of files to match explicitly is large.

The benchmark below are run in the following configuration :
 # data-env-vars.name             = mozilla-central-2018-08-01-zstd-sparse-revlog
 # benchmark.name                 = files
 # benchmark.variants.rev         = tip
 # benchmark.variants.files       = all-list-filepath-sorted
 # bin-env-vars.hg.flavor         = no-rust

It also includes timings using the re2 engine (through the `google-re2` module)
to show how much can be saved by just using a better regexp engine.


Pattern                time (seconds)        time using re2
-----------------------------------------------------------
just "."                0.4                    0.4
list of "filepath:…"    1.3                    1.3
list of "path:…"       25.7                    3.9
list of patterns       29.7                   10.4

As you can see, Without re2, using "filepath:" instead of "path:" is a huge
win. With re2, it is still about three times faster to not have to build the
regex.

# node.py - basic nodeid manipulation for mercurial
#
# Copyright 2005, 2006 Olivia 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.


import binascii

# This ugly style has a noticeable effect in manifest parsing
hex = binascii.hexlify
bin = binascii.unhexlify


def short(node):
    return hex(node[:6])


nullrev = -1

# pseudo identifier for working directory
# (experimental, so don't add too many dependencies on it)
wdirrev = 0x7FFFFFFF


class sha1nodeconstants:
    nodelen = 20

    # In hex, this is '0000000000000000000000000000000000000000'
    nullid = b"\0" * nodelen
    nullhex = hex(nullid)

    # Phony node value to stand-in for new files in some uses of
    # manifests.
    # In hex, this is '2121212121212121212121212121212121212121'
    newnodeid = b'!!!!!!!!!!!!!!!!!!!!'
    # In hex, this is '3030303030303030303030303030306164646564'
    addednodeid = b'000000000000000added'
    # In hex, this is '3030303030303030303030306d6f646966696564'
    modifiednodeid = b'000000000000modified'

    wdirfilenodeids = {newnodeid, addednodeid, modifiednodeid}

    # pseudo identifier for working directory
    # (experimental, so don't add too many dependencies on it)
    # In hex, this is 'ffffffffffffffffffffffffffffffffffffffff'
    wdirid = b"\xff" * nodelen
    wdirhex = hex(wdirid)


# legacy starting point for porting modules
nullid = sha1nodeconstants.nullid
nullhex = sha1nodeconstants.nullhex
newnodeid = sha1nodeconstants.newnodeid
addednodeid = sha1nodeconstants.addednodeid
modifiednodeid = sha1nodeconstants.modifiednodeid
wdirfilenodeids = sha1nodeconstants.wdirfilenodeids
wdirid = sha1nodeconstants.wdirid
wdirhex = sha1nodeconstants.wdirhex