Write You A Git (wyag教程)

#!/usr/bin/env python3

import libwyag
libwyag.main()

import argparse
import collections
import configparser
from datetime import datetime
import grp, pwd
from fnmatch import fnmatch
import hashlib
from math import ceil
import os
import re
import sys
import zlib

argparser = argparse.ArgumentParser(description="The stupidest content tracker")
argsubparsers = argparser.add_subparsers(title="Commands", dest="command")
argsubparsers.required = True

def main(argv=sys.argv[1:]):
    args = argparser.parse_args(argv)
    match args.command:
        case "add"          : cmd_add(args)
        case "cat-file"     : cmd_cat_file(args)
        case "check-ignore" : cmd_check_ignore(args)
        case "checkout"     : cmd_checkout(args)
        case "commit"       : cmd_commit(args)
        case "hash-object"  : cmd_hash_object(args)
        case "init"         : cmd_init(args)
        case "log"          : cmd_log(args)
        case "ls-files"     : cmd_ls_files(args)
        case "ls-tree"      : cmd_ls_tree(args)
        case "rev-parse"    : cmd_rev_parse(args)
        case "rm"           : cmd_rm(args)
        case "show-ref"     : cmd_show_ref(args)
        case "status"       : cmd_status(args)
        case "tag"          : cmd_tag(args)
        case _              : print("Bad command.")

class GitRepository(object):
    """A git repo!"""

    worktree = None
    gitdir = None
    conf = None

    def __init__(self, path, force=False):
        self.worktree = path
        self.gitdir = os.path.join(path, ".git")
        
        if not (force or os.path.isdir(self.gitdir)):
            raise Exception("Not a Git repo %s" % path)

        self.conf = configparse.ConfigParser()
        cfdir = repo_file(self, "config")

        if cfdir and os.path.exists(cfdir):
            self.conf.read([cfdir])
        elif not force:
            raise Exception("Configuration file missing")
        
        if not force:
            vers = int(self.conf.get("core", "repositoryformatversion"))
            if vers != 0:
                raise Exception("Unsupported repositoryformatversion %s" % vers)

def repo_path(repo, *path):
    """Compute path under repo's gitdir."""
    return os.join(repo.gitdir, path)

def repo_file(repo, *path, mkdir=False):
    """Same as repo_path, but create dirname(*path) if absent.  For
example, repo_file(r, \"refs\", \"remotes\", \"origin\", \"HEAD\") will create
.git/refs/remotes/origin."""
    if repo_dir(repo, *path[:-1], mkdir=mkdir):
        return repo_path(repo, *path)
    
def repo_dir(repo, *path, mkdir=False):
    """Same as repo_path, but mkdir *path if absent if mkdir."""
    
    path = repo_path(repo, *path)

    if os.path.exists(path):
        if (os.path.isdir(path)):
            return path
        else:
            raise Exception("Not a directory %s" % path)
    
    if mkdir:
        os.makedirs(path)
        return path
    else:
        return None

def repo_create(path):
    """Create a new repo at path"""

    repo = GitRepository(path, True)

    # First, make sure path isn't exist

    if os.path.exists(repo.worktree):
        if not os.path.isdir(repo.worktree):
            raise Exception("%s is not a directory!" % path)
        if os.path.exists(repo.gitdir) and os.listdir(repo.gitdir):
            raise Exception("%s is not empty!" % path)
    
    else:
        os.makedirs(repo.worktree)
    
    assert repo_dir(repo, "branches", mkdir=True)
    assert repo_dir(repo, "objects", mkdir=True)
    assert repo_dir(repo, "refs", "tags", mkdir=True)
    assert repo_dir(repo, "refs", "heads", mkdir=True)

    # Second, init them
    # .git/description
    with open(repo_file(repo, "description"), "w") as f:
        f.write("Unnamed repository; edit this file 'description' to name the repository.\n")

    # .git/HEAD
    with open(repo_file(repo, "HEAD"), "w") as f:
        f.write("ref: refs/heads/master\n")

    with open(repo_file(repo, "config"), "w") as f:
        config = repo_default_config()
        config.write(f)

    return repo

def repo_default_config():
    ret = configparser.ConfigParser()

    ret.add_section("core")
    ret.set("core", "repositoryformatversion", "0")
    ret.set("core", "filemode", "false")
    ret.set("core", "bare", "false")

    return ret

argsp = argsubparsers.add_parser("init", help="Initialize a new, empty repository.")
argsp.add_argument("path",
               metavar="directory",
               nargs="?",
               default=".",
               help="Where to create the repository.")

def cmd_init(args):
    repo_create(args.path)

def repo_find(path=".", required=True):
    path = os.path.realpath(path)

    if os.path.isdir(os.path.join(path, ".git")):
        return GitRepository(path)

    # If we haven't returned, recurse in parent, if w
    parent = os.path.realpath(os.path.join(path, ".."))

    if parent == path:
        # Bottom case
        # os.path.join("/", "..") == "/":
        # If parent==path, then path is root.
        if required:
            raise Exception("No git directory.")
        else:
            return None

    # Recursive case
    return repo_find(parent, required)

class GitObject(object):
    def __init__(self, data=None):
        if data != None:
            self.deserialize(data)
        else:
            self.init()
    
    def serialize(self, repo):
        """This function MUST be implemented by subclasses.

It must read the object's contents from self.data, a byte string, and do
whatever it takes to convert it into a meaningful representation.  What exactly that means depend on each subclass."""
        raise NotImplementedError()
    
    def deserialize(self, data):
        raise NotImplementedError()

    def init(self):
        pass

def object_read(repo, sha):
    """Read object sha from Git repository repo.  Return a
    GitObject whose exact type depends on the object."""

    path = repo_file(repo, "objects", sha[:2], sha[2:])

    if not os.path.isfile(path):
        return None

    with open(path, "rb") as f:
        raw = zlib.decompress(f.read())
        
        # Read object type
        x = raw.find(b' ')
        fmt = raw[0:x]

        # Read and validate object size
        y = raw.find(b'\x00', x)
        size = int(raw[x:y].decode("ascii"))
        if size != len(raw) - y -1:
            raise Exception("Malformed object {0}: bad length".format(sha))
        
        # Pick constructor
        match fmt:
            case b'commit' : c=GitCommit
            case b'tree'   : c=GitTree
            case b'tag'    : c=GitTag
            case b'blob'   : c=GitBlob
            case _:
                raise Exception("Unknown type {0} for object {1}".format(fmt.decode("ascii"), sha))

        # Call constructor and return object
        return c(raw[y+1:])

def object_write(obj, repo=None):
    # Serialize object data
    data = obj.serialize()
    # Add header
    result = obj.fmt + b' ' + str(len(data)).encode() + b'\x00' + data
    # Compute hash
    sha = hashlib.sha1(result).hexdigest()

    if repo:
        # Compute path
        path=repo_file(repo, "objects", sha[0:2], sha[2:], mkdir=True)

        if not os.path.exists(path):
            with open(path, 'wb') as f:
                # Compress and write
                f.write(zlib.compress(result))
    return sha

class GitBlob(GitObject):
    fmt=b'blob'

    def serialize(self):
        return self.blobdata

    def deserialize(self, data):
        self.blobdata = data

wyag cat-file TYPE OBJECT

argsp = argsubparsers.add_parser("cat-file",
                                 help="Provide content of repository objects")

argsp.add_argument("type",
                   metavar="type",
                   choices=["blob", "commit", "tag", "tree"],
                   help="Specify the type")

argsp.add_argument("object",
                   metavar="object",
                   help="The object to display")

def cmd_cat_file(args):
    repo = repo_find()
    cat_file(repo, args.object, fmt=args.type.encode())

def cat_file(repo, obj, fmt=None):
    obj = object_read(repo, object_find(repo, obj, fmt=fmt))
    sys.stdout.buffer.write(obj.serialize())

def object_find(repo, name, fmt=None, follow=True):
    return name

wyag hash-object [-w] [-t TYPE] FILE

argsp = argsubparsers.add_parser(
    "hash-object",
    help="Compute object ID and optionally creates a blob from a file")

argsp.add_argument("-t",
                   metavar="type",
                   dest="type",
                   choices=["blob", "commit", "tag", "tree"],
                   default="blob",
                   help="Specify the type")

argsp.add_argument("-w",
                   dest="write",
                   action="store_true",
                   help="Actually write the object into the database")

argsp.add_argument("path",
                   help="Read object from <file>")

def cmd_hash_object(args):
    if args.write:
        repo = repo_find()
    else:
        repo = None

    with open(args.path, "rb") as fd:
        sha = object_hash(fd, args.type.encode(), repo)
        print(sha)

def object_hash(fd, fmt, repo=None):
    """ Hash object, writing it to repo if provided."""
    data = fd.read()
	
    match fmt:
        case b'commit' : obj=GitCommit(data)
        case b'tree'   : obj=GitTree(data)
        case b'tag'    : obj=GitTag(data)
        case b'blob'   : obj=GitBlob(data)
        case _: raise Exception("Unknown type %s!" % fmt)

    return object_write(obj, repo)

def kvlm_parse(raw, start=0, dct=None):
    if not dct:
        dct = collections.OrderedDict()
        # You CANNOT declare the argument as dct=OrderedDict() or all
        # call to the functions will endlessly grow the same dict.

        # This function is recursive: it reads a key/value pair, then call
        # itself back with the new position.  So we first need to know
        # where we are: at a keyword, or already in the messageQ

        # We search for the next space and the next newline.
        spc = raw.find(b" ", start)
        nl = raw.find(b'\n', start)

        # If space appears before newline, we have a keyword. Otherwise,
        # it's the final message, which we just read to the end of the file.

        # Base case
        # =========
        # If newline appears first (or there's no space at all, in which
        # case find returns -1), we assume a blank line.  A blank line
        # means the remainder of the data is the message.  We store it in
        # the dictionary, with None as the key, and return.
        if (spc < 0) or (nl < spc):
            assert nl == start
            dct[None] = raw[start+1:]
            return dct
        
        # Recursive case
        # ==============
        # we read a key-value pair and recurse for the next.
        key = raw[start:spc]

        # Find the end of the value.  Continuation lines begin with a
        # space, so we loop until we find a "\n" not followed by a space.
        end = start
        while True:
            end = raw.find(b'\n', end+1)
            if raw[end+1] != ord(' '): break

        # Grab the value
        # Also, drop the leading space on continuation lines
        value = raw[spc+1:end].replace(b'\n ', b'\n')

        # Don't overwrite existing data contents
        if key in dct:
            if type(dct[key]) == list:
                dct[key].append(value)
            else:
                dct[key] = [ dct[key], value ]
        else:
            dct[key]=value

        return kvlm_parse(raw, start=end+1, dct=dct)

def kvlm_serialize(kvlm):
    ret = b''

    # Output fields
    for k in kvlm.keys():
        # Skip the message itself
        if k == None: continue
        val = kvlm[k]
        # Normalize to a list
        if type(val) != list:
            val = [ val ]

        for v in val:
            ret += k + b' ' + (v.replace(b'\n', b'\n ')) + b'\n'

    # Append message
    ret += b'\n' + kvlm[None] + b'\n'

    return ret

class GitCommit(GitObject):
    fmt=b'commit'

    def deserialize(self, data):
        self.kvlm = kvlm_parse(data)

    def serialize(self):
        return kvlm_serialize(self.kvlm)

    def init(self):
        self.kvlm = dict()

argsp = argsubparsers.add_parser("log", help="Display history of a given commit.")
argsp.add_argument("commit",
                   default="HEAD",
                   nargs="?",
                   help="Commit to start at.")



def cmd_log(args):
    repo = repo_find()

    print("digraph wyaglog{")
    print("  node[shape=rect]")
    log_graphviz(repo, object_find(repo, args.commit), set())
    print("}")

def log_graphviz(repo, sha, seen):

    if sha in seen:
        return
    seen.add(sha)

    commit = object_read(repo, sha)
    short_hash = sha[0:8]
    message = commit.kvlm[None].decode("utf8").strip()
    message = message.replace("\\", "\\\\")
    message = message.replace("\"", "\\\"")

    if "\n" in message: # Keep only the first line
        message = message[:message.index("\n")]

    print("  c_{0} [label=\"{1}: {2}\"]".format(sha, sha[0:7], message))
    assert commit.fmt==b'commit'

    if not b'parent' in commit.kvlm.keys():
        # Base case: the initial commit.
        return

    parents = commit.kvlm[b'parent']

    if type(parents) != list:
        parents = [ parents ]

    for p in parents:
        p = p.decode("ascii")
        print ("  c_{0} -> c_{1};".format(sha, p))
        log_graphviz(repo, p, seen)

wyag log e03158242ecab460f31b0d6ae1642880577ccbe8 > log.dot
dot -O -Tpdf log.dot

class GitTreeLeaf (object):
    def __init__(self, mode, path, sha):
        self.mode = mode
        self.path = path
        self.sha = sha

def tree_parse_one(raw, start=0):
    # Find the space terminator of the mode
    x = raw.find(b' ', start)
    assert x-start == 5 or x-start==6

    # Read the mode
    mode = raw[start:x]
    if len(mode) == 5:
        # Normalize to six bytes.
        mode = b" " + mode

    # Find the NULL terminator of the path
    y = raw.find(b'\x00', x)
    # and read the path
    path = raw[x+1:y]

    # Read the SHA and convert to a hex string
    sha = format(int.from_bytes(raw[y+1:y+21], "big"), "040x")
    return y+21, GitTreeLeaf(mode, path.decode("utf8"), sha)

def tree_parse(raw):
    pos = 0
    max = len(raw)
    ret = list()
    while pos < max:
        pos, data = tree_parse_one(raw, pos)
        ret.append(data)

    return ret

# Notice this isn't a comparison function, but a conversion function.
# Python's default sort doesn't accept a custom comparison function,
# like in most languages, but a `key` arguments that returns a new
# value, which is compared using the default rules.  So we just return
# the leaf name, with an extra / if it's a directory.
def tree_leaf_sort_key(leaf):
    if leaf.mode.startswith(b"10"):
        return leaf.path
    else:
        return leaf.path + "/"

def tree_serialize(obj):
    obj.items.sort(key=tree_leaf_sort_key)
    ret = b''
    for i in obj.items:
        ret += i.mode
        ret += b' '
        ret += i.path.encode("utf8")
        ret += b'\x00'
        sha = int(i.sha, 16)
        ret += sha.to_bytes(20, byteorder="big")
    return ret

class GitTree(GitObject):
    fmt=b'tree'

    def deserialize(self, data):
        self.items = tree_parse(data)

    def serialize(self):
        return tree_serialize(self)

    def init(self):
        self.items = list()

git ls-tree [-r] TREE

argsp = argsubparsers.add_parser("ls-tree", help="Pretty-print a tree object.")
argsp.add_argument("-r",
                   dest="recursive",
                   action="store_true",
                   help="Recurse into sub-trees")

argsp.add_argument("tree",
                   help="A tree-ish object.")

def cmd_ls_tree(args):
    repo = repo_find()
    ls_tree(repo, args.tree, args.recursive)

def ls_tree(repo, ref, recursive=None, prefix=""):
    sha = object_find(repo, ref, fmt=b"tree")
    obj = object_read(repo, sha)
    for item in obj.items:
        if len(item.mode) == 5:
            type = item.mode[0:1]
        else:
            type = item.mode[0:2]

        match type: # Determine the type.
            case b'04': type = "tree"
            case b'10': type = "blob" # A regular file.
            case b'12': type = "blob" # A symlink. Blob contents is link target.
            case b'16': type = "commit" # A submodule
            case _: raise Exception("Weird tree leaf mode {}".format(item.mode))

        if not (recursive and type=='tree'): # This is a leaf
            print("{0} {1} {2}\t{3}".format(
                "0" * (6 - len(item.mode)) + item.mode.decode("ascii"),
                # Git's ls-tree displays the type
                # of the object pointed to.  We can do that too :)
                type,
                item.sha,
                os.path.join(prefix, item.path)))
        else: # This is a branch, recurse
            ls_tree(repo, item.sha, recursive, os.path.join(prefix, item.path))

argsp = argsubparsers.add_parser("checkout", help="Checkout a commit inside of a directory.")

argsp.add_argument("commit",
                   help="The commit or tree to checkout.")

argsp.add_argument("path",
                   help="The EMPTY directory to checkout on.")

def cmd_checkout(args):
    repo = repo_find()

    obj = object_read(repo, object_find(repo, args.commit))

    # If the object is a commit, we grab its tree
    if obj.fmt == b'commit':
        obj = object_read(repo, obj.kvlm[b'tree'].decode("ascii"))

    # Verify that path is an empty directory
    if os.path.exists(args.path):
        if not os.path.isdir(args.path):
            raise Exception("Not a directory {0}!".format(args.path))
        if os.listdir(args.path):
            raise Exception("Not empty {0}!".format(args.path))
    else:
        os.makedirs(args.path)

    tree_checkout(repo, obj, os.path.realpath(args.path))

def tree_checkout(repo, tree, path):
    for item in tree.items:
        obj = object_read(repo, item.sha)
        dest = os.path.join(path, item.path)

        if obj.fmt == b'tree':
            os.mkdir(dest)
            tree_checkout(repo, obj, dest)
        elif obj.fmt == b'blob':
            # @TODO Support symlinks (identified by mode 12****)
            with open(dest, 'wb') as f:
                f.write(obj.blobdata)

6071c08bcb4757d8c89a30d9755d2466cef8c1de

def ref_resolve(repo, ref):
    path = repo_file(repo, ref)

    # Sometimes, an indirect reference may be broken.  This is normal
    # in one specific case: we're looking for HEAD on a new repository
    # with no commits.  In that case, .git/HEAD points to "ref:
    # refs/heads/main", but .git/refs/heads/main doesn't exist yet
    # (since there's no commit for it to refer to).
    if not os.path.isfile(path):
        return None

    with open(path, 'r') as fp:
        data = fp.read()[:-1]
        # Drop final \n ^^^^^
    if data.startswith("ref: "):
        return ref_resolve(repo, data[5:])
    else:
        return data

def ref_list(repo, path=None):
    if not path:
        path = repo_dir(repo, "refs")
    ret = collections.OrderedDict()
    # Git shows refs sorted.  To do the same, we use
    # an OrderedDict and sort the output of listdir
    for f in sorted(os.listdir(path)):
        can = os.path.join(path, f)
        if os.path.isdir(can):
            ret[f] = ref_list(repo, can)
        else:
            ret[f] = ref_resolve(repo, can)

    return ret

argsp = argsubparsers.add_parser("show-ref", help="List references.")

def cmd_show_ref(args):
    repo = repo_find()
    refs = ref_list(repo)
    show_ref(repo, refs, prefix="refs")

def show_ref(repo, refs, with_hash=True, prefix=""):
    for k, v in refs.items():
        if type(v) == str:
            print ("{0}{1}{2}".format(
                v + " " if with_hash else "",
                prefix + "/" if prefix else "",
                k))
        else:
            show_ref(repo, v, with_hash=with_hash, prefix="{0}{1}{2}".format(prefix, "/" if prefix else "", k))

git tag v12.78.52 6071c08
# the object hash ^here^^ is optional and defaults to HEAD.

git checkout v12.78.52
git checkout 6071c08

class GitTag(GitCommit):
    fmt = b'tag'

git tag                  # List all tags
git tag NAME [OBJECT]    # create a new *lightweight* tag NAME, pointing
                         # at HEAD (default) or OBJECT
git tag -a NAME [OBJECT] # create a new tag *object* NAME, pointing at
                         # HEAD (default) or OBJECT

argsp = argsubparsers.add_parser(
    "tag",
    help="List and create tags")

argsp.add_argument("-a",
                   action="store_true",
                   dest="create_tag_object",
                   help="Whether to create a tag object")

argsp.add_argument("name",
                   nargs="?",
                   help="The new tag's name")

argsp.add_argument("object",
                   default="HEAD",
                   nargs="?",
                   help="The object the new tag will point to")

def cmd_tag(args):
    repo = repo_find()

    if args.name:
        tag_create(repo,
                   args.name,
                   args.object,
                   type="object" if args.create_tag_object else "ref")
    else:
        refs = ref_list(repo)
        show_ref(repo, refs["tags"], with_hash=False)

def tag_create(repo, name, ref, create_tag_object=False):
    # get the GitObject from the object reference
    sha = object_find(repo, ref)

    if create_tag_object:
        # create tag object (commit)
        tag = GitTag(repo)
        tag.kvlm = collections.OrderedDict()
        tag.kvlm[b'object'] = sha.encode()
        tag.kvlm[b'type'] = b'commit'
        tag.kvlm[b'tag'] = name.encode()
        # Feel free to let the user give their name!
        # Notice you can fix this after commit, read on!
        tag.kvlm[b'tagger'] = b'Wyag <wyag@example.com>'
        # …and a tag message!
        tag.kvlm[None] = b"A tag generated by wyag, which won't let you customize the message!"
        tag_sha = object_write(tag)
        # create reference
        ref_create(repo, "tags/" + name, tag_sha)
    else:
        # create lightweight tag (ref)
        ref_create(repo, "tags/" + name, sha)

def ref_create(repo, ref_name, sha):
    with open(repo_file(repo, "refs/" + ref_name), 'w') as fp:
        fp.write(sha + "\n")

def object_resolve(repo, name):
    """Resolve name to an object hash in repo.

This function is aware of:

 - the HEAD literal
    - short and long hashes
    - tags
    - branches
    - remote branches"""
    candidates = list()
    hashRE = re.compile(r"^[0-9A-Fa-f]{4,40}$")

    # Empty string?  Abort.
    if not name.strip():
        return None

    # Head is nonambiguous
    if name == "HEAD":
        return [ ref_resolve(repo, "HEAD") ]

    # If it's a hex string, try for a hash.
    if hashRE.match(name):
        # This may be a hash, either small or full.  4 seems to be the
        # minimal length for git to consider something a short hash.
        # This limit is documented in man git-rev-parse
        name = name.lower()
        prefix = name[0:2]
        path = repo_dir(repo, "objects", prefix, mkdir=False)
        if path:
            rem = name[2:]
            for f in os.listdir(path):
                if f.startswith(rem):
                    # Notice a string startswith() itself, so this
                    # works for full hashes.
                    candidates.append(prefix + f)

    # Try for references.
    as_tag = ref_resolve(repo, "refs/tags/" + name)
    if as_tag: # Did we find a tag?
        candidates.append(as_tag)

    as_branch = ref_resolve(repo, "refs/heads/" + name)
    if as_branch: # Did we find a branch?
        candidates.append(as_branch)

    return candidates

def object_find(repo, name, fmt=None, follow=True):
      sha = object_resolve(repo, name)

      if not sha:
          raise Exception("No such reference {0}.".format(name))

      if len(sha) > 1:
          raise Exception("Ambiguous reference {0}: Candidates are:\n - {1}.".format(name,  "\n - ".join(sha)))

      sha = sha[0]

      if not fmt:
          return sha

      while True:
          obj = object_read(repo, sha)
          #     ^^^^^^^^^^^ < this is a bit agressive: we're reading
          # the full object just to get its type.  And we're doing
          # that in a loop, albeit normally short.  Don't expect
          # high performance here.

          if obj.fmt == fmt:
              return sha

          if not follow:
              return None

          # Follow tags
          if obj.fmt == b'tag':
                sha = obj.kvlm[b'object'].decode("ascii")
          elif obj.fmt == b'commit' and fmt == b'tree':
                sha = obj.kvlm[b'tree'].decode("ascii")
          else:
              return None

argsp = argsubparsers.add_parser(
    "rev-parse",
    help="Parse revision (or other objects) identifiers")

argsp.add_argument("--wyag-type",
                   metavar="type",
                   dest="type",
                   choices=["blob", "commit", "tag", "tree"],
                   default=None,
                   help="Specify the expected type")

argsp.add_argument("name",
                   help="The name to parse")

def cmd_rev_parse(args):
    if args.type:
        fmt = args.type.encode()
    else:
        fmt = None

    repo = repo_find()

    print (object_find(repo, args.name, fmt, follow=True))

class GitIndexEntry (object):
    def __init__(self, ctime=None, mtime=None, dev=None, ino=None,
                 mode_type=None, mode_perms=None, uid=None, gid=None,
                 fsize=None, sha=None, flag_assume_valid=None,
                 flag_stage=None, name=None):
      # The last time a file's metadata changed.  This is a pair
      # (timestamp in seconds, nanoseconds)
      self.ctime = ctime
      # The last time a file's data changed.  This is a pair
      # (timestamp in seconds, nanoseconds)
      self.mtime = mtime
      # The ID of device containing this file
      self.dev = dev
      # The file's inode number
      self.ino = ino
      # The object type, either b1000 (regular), b1010 (symlink),
      # b1110 (gitlink).
      self.mode_type = mode_type
      # The object permissions, an integer.
      self.mode_perms = mode_perms
      # User ID of owner
      self.uid = uid
      # Group ID of ownner
      self.gid = gid
      # Size of this object, in bytes
      self.fsize = fsize
      # The object's SHA
      self.sha = sha
      self.flag_assume_valid = flag_assume_valid
      self.flag_stage = flag_stage
      # Name of the object (full path this time!)
      self.name = name

class GitIndex (object):
    version = None
    entries = []
    # ext = None
    # sha = None

    def __init__(self, version=2, entries=None):
        if not entries:
            entries = list()

        self.version = version
        self.entries = entries

def index_read(repo):
    index_file = repo_file(repo, "index")

    # New repositories have no index!
    if not os.path.exists(index_file):
        return GitIndex()

    with open(index_file, 'rb') as f:
        raw = f.read()

    header = raw[:12]
    signature = header[:4]
    assert signature == b"DIRC" # Stands for "DirCache"
    version = int.from_bytes(header[4:8], "big")
    assert version == 2, "wyag only supports index file version 2"
    count = int.from_bytes(header[8:12], "big")

    entries = list()

    content = raw[12:]
    idx = 0
    for i in range(0, count):
        # Read creation time, as a unix timestamp (seconds since
        # 1970-01-01 00:00:00, the "epoch")
        ctime_s =  int.from_bytes(content[idx: idx+4], "big")
        # Read creation time, as nanoseconds after that timestamps,
        # for extra precision.
        ctime_ns = int.from_bytes(content[idx+4: idx+8], "big")
        # Same for modification time: first seconds from epoch.
        mtime_s = int.from_bytes(content[idx+8: idx+12], "big")
        # Then extra nanoseconds
        mtime_ns = int.from_bytes(content[idx+12: idx+16], "big")
        # Device ID
        dev = int.from_bytes(content[idx+16: idx+20], "big")
        # Inode
        ino = int.from_bytes(content[idx+20: idx+24], "big")
        # Ignored.
        unused = int.from_bytes(content[idx+24: idx+26], "big")
        assert 0 == unused
        mode = int.from_bytes(content[idx+26: idx+28], "big")
        mode_type = mode >> 12
        assert mode_type in [0b1000, 0b1010, 0b1110]
        mode_perms = mode & 0b0000000111111111
        # User ID
        uid = int.from_bytes(content[idx+28: idx+32], "big")
        # Group ID
        gid = int.from_bytes(content[idx+32: idx+36], "big")
        # Size
        fsize = int.from_bytes(content[idx+36: idx+40], "big")
        # SHA (object ID).  We'll store it as a lowercase hex string
        # for consistency.
        sha = format(int.from_bytes(content[idx+40: idx+60], "big"), "040x")
        # Flags we're going to ignore
        flags = int.from_bytes(content[idx+60: idx+62], "big")
        # Parse flags
        flag_assume_valid = (flags & 0b1000000000000000) != 0
        flag_extended = (flags & 0b0100000000000000) != 0
        assert not flag_extended
        flag_stage =  flags & 0b0011000000000000
        # Length of the name.  This is stored on 12 bits, some max
        # value is 0xFFF, 4095.  Since names can occasionally go
        # beyond that length, git treats 0xFFF as meaning at least
        # 0xFFF, and looks for the final 0x00 to find the end of the
        # name --- at a small, and probably very rare, performance
        # cost.
        name_length = flags & 0b0000111111111111

        # We've read 62 bytes so far.
        idx += 62

        if name_length < 0xFFF:
            assert content[idx + name_length] == 0x00
            raw_name = content[idx:idx+name_length]
            idx += name_length + 1
        else:
            print("Notice: Name is 0x{:X} bytes long.".format(name_length))
            # This probably wasn't tested enough.  It works with a
            # path of exactly 0xFFF bytes.  Any extra bytes broke
            # something between git, my shell and my filesystem.
            null_idx = content.find(b'\x00', idx + 0xFFF)
            raw_name = content[idx: null_idx]
            idx = null_idx + 1

        # Just parse the name as utf8.
        name = raw_name.decode("utf8")

        # Data is padded on multiples of eight bytes for pointer
        # alignment, so we skip as many bytes as we need for the next
        # read to start at the right position.

        idx = 8 * ceil(idx / 8)

        # And we add this entry to our list.
        entries.append(GitIndexEntry(ctime=(ctime_s, ctime_ns),
                                     mtime=(mtime_s,  mtime_ns),
                                     dev=dev,
                                     ino=ino,
                                     mode_type=mode_type,
                                     mode_perms=mode_perms,
                                     uid=uid,
                                     gid=gid,
                                     fsize=fsize,
                                     sha=sha,
                                     flag_assume_valid=flag_assume_valid,
                                     flag_stage=flag_stage,
                                     name=name))

    return GitIndex(version=version, entries=entries)

argsp = argsubparsers.add_parser("ls-files", help = "List all the stage files")
argsp.add_argument("--verbose", action="store_true", help="Show everything.")

def cmd_ls_files(args):
  repo = repo_find()
  index = index_read(repo)
  if args.verbose:
    print("Index file format v{}, containing {} entries.".format(index.version, len(index.entries)))

  for e in index.entries:
    print(e.name)
    if args.verbose:
      print("  {} with perms: {:o}".format(
        { 0b1000: "regular file",
          0b1010: "symlink",
          0b1110: "git link" }[e.mode_type],
        e.mode_perms))
      print("  on blob: {}".format(e.sha))
      print("  created: {}.{}, modified: {}.{}".format(
        datetime.fromtimestamp(e.ctime[0])
        , e.ctime[1]
        , datetime.fromtimestamp(e.mtime[0])
        , e.mtime[1]))
      print("  device: {}, inode: {}".format(e.dev, e.ino))
      print("  user: {} ({})  group: {} ({})".format(
        pwd.getpwuid(e.uid).pw_name,
        e.uid,
        grp.getgrgid(e.gid).gr_name,
        e.gid))
      print("  flags: stage={} assume_valid={}".format(
        e.flag_stage,
        e.flag_assume_valid))

argsp = argsubparsers.add_parser("check-ignore", help = "Check path(s) against ignore rules.")
argsp.add_argument("path", nargs="+", help="Paths to check")


def cmd_check_ignore(args):
  repo = repo_find()
  rules = gitignore_read(repo)
  for path in args.path:
      if check_ignore(rules, path):
        print(path)