[StGit PATCH 1/5] New StGit core infrastructure: repository operations

["Karl Hasselström" <kha@treskal.com>]

This is the first part of the New and Improved StGit core
infrastructure. It has functions for manipulating the git repository
(commits, refs, and so on), but doesn't yet touch the index or
worktree.

Currently not used by anything.

Signed-off-by: Karl Hasselström <kha@treskal.com>

---

 stgit/lib/__init__.py    |   18 +++
 stgit/lib/git.py         |  245 ++++++++++++++++++++++++++++++++++++++++++++++
 stgit/lib/stack.py       |  121 +++++++++++++++++++++++
 stgit/lib/transaction.py |   79 +++++++++++++++
 stgit/utils.py           |   13 ++
 5 files changed, 476 insertions(+), 0 deletions(-)
 create mode 100644 stgit/lib/__init__.py
 create mode 100644 stgit/lib/git.py
 create mode 100644 stgit/lib/stack.py
 create mode 100644 stgit/lib/transaction.py


diff --git a/stgit/lib/__init__.py b/stgit/lib/__init__.py
new file mode 100644
index 0000000..45eb307
--- /dev/null
+++ b/stgit/lib/__init__.py
@@ -0,0 +1,18 @@
+# -*- coding: utf-8 -*-
+
+__copyright__ = """
+Copyright (C) 2007, Karl Hasselström <kha@treskal.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License version 2 as
+published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+"""
diff --git a/stgit/lib/git.py b/stgit/lib/git.py
new file mode 100644
index 0000000..1b873e3
--- /dev/null
+++ b/stgit/lib/git.py
@@ -0,0 +1,245 @@
+import os, os.path, re
+from stgit import exception, run, utils
+
+class RepositoryException(exception.StgException):
+    pass
+
+class DetachedHeadException(RepositoryException):
+    pass
+
+class Repr(object):
+    def __repr__(self):
+        return str(self)
+
+class NoValue(object):
+    pass
+
+def make_defaults(defaults):
+    def d(val, attr):
+        if val != NoValue:
+            return val
+        elif defaults != NoValue:
+            return getattr(defaults, attr)
+        else:
+            return None
+    return d
+
+class Person(Repr):
+    """Immutable."""
+    def __init__(self, name = NoValue, email = NoValue,
+                 date = NoValue, defaults = NoValue):
+        d = make_defaults(defaults)
+        self.__name = d(name, 'name')
+        self.__email = d(email, 'email')
+        self.__date = d(date, 'date')
+    name = property(lambda self: self.__name)
+    email = property(lambda self: self.__email)
+    date = property(lambda self: self.__date)
+    def set_name(self, name):
+        return type(self)(name = name, defaults = self)
+    def set_email(self, email):
+        return type(self)(email = email, defaults = self)
+    def set_date(self, date):
+        return type(self)(date = date, defaults = self)
+    def __str__(self):
+        return '%s <%s> %s' % (self.name, self.email, self.date)
+    @classmethod
+    def parse(cls, s):
+        m = re.match(r'^([^<]*)<([^>]*)>\s+(\d+\s+[+-]\d{4})$', s)
+        assert m
+        name = m.group(1).strip()
+        email = m.group(2)
+        date = m.group(3)
+        return cls(name, email, date)
+
+class Tree(Repr):
+    """Immutable."""
+    def __init__(self, sha1):
+        self.__sha1 = sha1
+    sha1 = property(lambda self: self.__sha1)
+    def __str__(self):
+        return 'Tree<%s>' % self.sha1
+
+class Commitdata(Repr):
+    """Immutable."""
+    def __init__(self, tree = NoValue, parents = NoValue, author = NoValue,
+                 committer = NoValue, message = NoValue, defaults = NoValue):
+        d = make_defaults(defaults)
+        self.__tree = d(tree, 'tree')
+        self.__parents = d(parents, 'parents')
+        self.__author = d(author, 'author')
+        self.__committer = d(committer, 'committer')
+        self.__message = d(message, 'message')
+    tree = property(lambda self: self.__tree)
+    parents = property(lambda self: self.__parents)
+    @property
+    def parent(self):
+        assert len(self.__parents) == 1
+        return self.__parents[0]
+    author = property(lambda self: self.__author)
+    committer = property(lambda self: self.__committer)
+    message = property(lambda self: self.__message)
+    def set_tree(self, tree):
+        return type(self)(tree = tree, defaults = self)
+    def set_parents(self, parents):
+        return type(self)(parents = parents, defaults = self)
+    def add_parent(self, parent):
+        return type(self)(parents = list(self.parents or []) + [parent],
+                          defaults = self)
+    def set_parent(self, parent):
+        return self.set_parents([parent])
+    def set_author(self, author):
+        return type(self)(author = author, defaults = self)
+    def set_committer(self, committer):
+        return type(self)(committer = committer, defaults = self)
+    def set_message(self, message):
+        return type(self)(message = message, defaults = self)
+    def __str__(self):
+        if self.tree == None:
+            tree = None
+        else:
+            tree = self.tree.sha1
+        if self.parents == None:
+            parents = None
+        else:
+            parents = [p.sha1 for p in self.parents]
+        return ('Commitdata<tree: %s, parents: %s, author: %s,'
+                ' committer: %s, message: "%s">'
+                ) % (tree, parents, self.author, self.committer, self.message)
+    @classmethod
+    def parse(cls, repository, s):
+        cd = cls()
+        lines = list(s.splitlines(True))
+        for i in xrange(len(lines)):
+            line = lines[i].strip()
+            if not line:
+                return cd.set_message(''.join(lines[i+1:]))
+            key, value = line.split(None, 1)
+            if key == 'tree':
+                cd = cd.set_tree(repository.get_tree(value))
+            elif key == 'parent':
+                cd = cd.add_parent(repository.get_commit(value))
+            elif key == 'author':
+                cd = cd.set_author(Person.parse(value))
+            elif key == 'committer':
+                cd = cd.set_committer(Person.parse(value))
+            else:
+                assert False
+        assert False
+
+class Commit(Repr):
+    """Immutable."""
+    def __init__(self, repository, sha1):
+        self.__sha1 = sha1
+        self.__repository = repository
+        self.__data = None
+    sha1 = property(lambda self: self.__sha1)
+    @property
+    def data(self):
+        if self.__data == None:
+            self.__data = Commitdata.parse(
+                self.__repository,
+                self.__repository.cat_object(self.sha1))
+        return self.__data
+    def __str__(self):
+        return 'Commit<sha1: %s, data: %s>' % (self.sha1, self.__data)
+
+class Refs(object):
+    def __init__(self, repository):
+        self.__repository = repository
+        self.__refs = None
+    def __cache_refs(self):
+        self.__refs = {}
+        for line in self.__repository.run(['git', 'show-ref']).output_lines():
+            m = re.match(r'^([0-9a-f]{40})\s+(\S+)$', line)
+            sha1, ref = m.groups()
+            self.__refs[ref] = sha1
+    def get(self, ref):
+        """Throws KeyError if ref doesn't exist."""
+        if self.__refs == None:
+            self.__cache_refs()
+        return self.__repository.get_commit(self.__refs[ref])
+    def set(self, ref, commit, msg):
+        if self.__refs == None:
+            self.__cache_refs()
+        old_sha1 = self.__refs.get(ref, '0'*40)
+        new_sha1 = commit.sha1
+        if old_sha1 != new_sha1:
+            self.__repository.run(['git', 'update-ref', '-m', msg,
+                                   ref, new_sha1, old_sha1]).no_output()
+            self.__refs[ref] = new_sha1
+    def delete(self, ref):
+        if self.__refs == None:
+            self.__cache_refs()
+        self.__repository.run(['git', 'update-ref',
+                               '-d', ref, self.__refs[ref]]).no_output()
+        del self.__refs[ref]
+
+class ObjectCache(object):
+    """Cache for Python objects, for making sure that we create only one
+    Python object per git object."""
+    def __init__(self, create):
+        self.__objects = {}
+        self.__create = create
+    def __getitem__(self, name):
+        if not name in self.__objects:
+            self.__objects[name] = self.__create(name)
+        return self.__objects[name]
+    def __contains__(self, name):
+        return name in self.__objects
+    def __setitem__(self, name, val):
+        assert not name in self.__objects
+        self.__objects[name] = val
+
+class RunWithEnv(object):
+    def run(self, args, env = {}):
+        return run.Run(*args).env(utils.add_dict(self.env, env))
+
+class Repository(RunWithEnv):
+    def __init__(self, directory):
+        self.__git_dir = directory
+        self.__refs = Refs(self)
+        self.__trees = ObjectCache(lambda sha1: Tree(sha1))
+        self.__commits = ObjectCache(lambda sha1: Commit(self, sha1))
+    env = property(lambda self: { 'GIT_DIR': self.__git_dir })
+    @classmethod
+    def default(cls):
+        """Return the default repository."""
+        try:
+            return cls(run.Run('git', 'rev-parse', '--git-dir'
+                               ).output_one_line())
+        except run.RunException:
+            raise RepositoryException('Cannot find git repository')
+    directory = property(lambda self: self.__git_dir)
+    refs = property(lambda self: self.__refs)
+    def cat_object(self, sha1):
+        return self.run(['git', 'cat-file', '-p', sha1]).raw_output()
+    def get_tree(self, sha1):
+        return self.__trees[sha1]
+    def get_commit(self, sha1):
+        return self.__commits[sha1]
+    def commit(self, commitdata):
+        c = ['git', 'commit-tree', commitdata.tree.sha1]
+        for p in commitdata.parents:
+            c.append('-p')
+            c.append(p.sha1)
+        env = {}
+        for p, v1 in ((commitdata.author, 'AUTHOR'),
+                       (commitdata.committer, 'COMMITTER')):
+            if p != None:
+                for attr, v2 in (('name', 'NAME'), ('email', 'EMAIL'),
+                                 ('date', 'DATE')):
+                    if getattr(p, attr) != None:
+                        env['GIT_%s_%s' % (v1, v2)] = getattr(p, attr)
+        sha1 = self.run(c, env = env).raw_input(commitdata.message
+                                                ).output_one_line()
+        return self.get_commit(sha1)
+    @property
+    def head(self):
+        try:
+            return self.run(['git', 'symbolic-ref', '-q', 'HEAD']
+                            ).output_one_line()
+        except run.RunException:
+            raise DetachedHeadException()
+    def set_head(self, ref, msg):
+        self.run(['git', 'symbolic-ref', '-m', msg, 'HEAD', ref]).no_output()
diff --git a/stgit/lib/stack.py b/stgit/lib/stack.py
new file mode 100644
index 0000000..b4d99ba
--- /dev/null
+++ b/stgit/lib/stack.py
@@ -0,0 +1,121 @@
+import os.path
+from stgit import utils
+from stgit.lib import git
+
+class Patch(object):
+    def __init__(self, stack, name):
+        self.__stack = stack
+        self.__name = name
+    name = property(lambda self: self.__name)
+    def __ref(self):
+        return 'refs/patches/%s/%s' % (self.__stack.name, self.__name)
+    @property
+    def commit(self):
+        return self.__stack.repository.refs.get(self.__ref())
+    def set_commit(self, commit, msg):
+        self.__stack.repository.refs.set(self.__ref(), commit, msg)
+    def delete(self):
+        self.__stack.repository.refs.delete(self.__ref())
+    def is_applied(self):
+        return self.name in self.__stack.patchorder.applied
+    def is_empty(self):
+        c = self.commit
+        return c.data.tree == c.data.parent.data.tree
+
+class PatchOrder(object):
+    """Keeps track of patch order, and which patches are applied.
+    Works with patch names, not actual patches."""
+    __list_order = [ 'applied', 'unapplied' ]
+    def __init__(self, stack):
+        self.__stack = stack
+        self.__lists = {}
+    def __read_file(self, fn):
+        return tuple(utils.read_strings(
+            os.path.join(self.__stack.directory, fn)))
+    def __write_file(self, fn, val):
+        utils.write_strings(os.path.join(self.__stack.directory, fn), val)
+    def __get_list(self, name):
+        if not name in self.__lists:
+            self.__lists[name] = self.__read_file(name)
+        return self.__lists[name]
+    def __set_list(self, name, val):
+        val = tuple(val)
+        if val != self.__lists.get(name, None):
+            self.__lists[name] = val
+            self.__write_file(name, val)
+    applied = property(lambda self: self.__get_list('applied'),
+                       lambda self, val: self.__set_list('applied', val))
+    unapplied = property(lambda self: self.__get_list('unapplied'),
+                         lambda self, val: self.__set_list('unapplied', val))
+
+class Patches(object):
+    """Creates Patch objects."""
+    def __init__(self, stack):
+        self.__stack = stack
+        def create_patch(name):
+            p = Patch(self.__stack, name)
+            p.commit # raise exception if the patch doesn't exist
+            return p
+        self.__patches = git.ObjectCache(create_patch) # name -> Patch
+    def exists(self, name):
+        try:
+            self.get(name)
+            return True
+        except KeyError:
+            return False
+    def get(self, name):
+        return self.__patches[name]
+    def new(self, name, commit, msg):
+        assert not name in self.__patches
+        p = Patch(self.__stack, name)
+        p.set_commit(commit, msg)
+        self.__patches[name] = p
+        return p
+
+class Stack(object):
+    def __init__(self, repository, name):
+        self.__repository = repository
+        self.__name = name
+        self.__patchorder = PatchOrder(self)
+        self.__patches = Patches(self)
+    name = property(lambda self: self.__name)
+    repository = property(lambda self: self.__repository)
+    patchorder = property(lambda self: self.__patchorder)
+    patches = property(lambda self: self.__patches)
+    @property
+    def directory(self):
+        return os.path.join(self.__repository.directory, 'patches', self.__name)
+    def __ref(self):
+        return 'refs/heads/%s' % self.__name
+    @property
+    def head(self):
+        return self.__repository.refs.get(self.__ref())
+    def set_head(self, commit, msg):
+        self.__repository.refs.set(self.__ref(), commit, msg)
+    @property
+    def base(self):
+        if self.patchorder.applied:
+            return self.patches.get(self.patchorder.applied[0]
+                                    ).commit.data.parent
+        else:
+            return self.head
+
+class Repository(git.Repository):
+    def __init__(self, *args, **kwargs):
+        git.Repository.__init__(self, *args, **kwargs)
+        self.__stacks = {} # name -> Stack
+    @property
+    def current_branch(self):
+        return utils.strip_leading('refs/heads/', self.head)
+    @property
+    def current_stack(self):
+        return self.get_stack(self.current_branch)
+    def get_stack(self, name):
+        if not name in self.__stacks:
+            if name == None:
+                s = None # detached HEAD
+            else:
+                # TODO: verify that the branch exists
+                s = Stack(self, name)
+            self.__stacks[name] = s
+        return self.__stacks[name]
diff --git a/stgit/lib/transaction.py b/stgit/lib/transaction.py
new file mode 100644
index 0000000..991e64e
--- /dev/null
+++ b/stgit/lib/transaction.py
@@ -0,0 +1,79 @@
+from stgit import exception
+from stgit.out import *
+
+class TransactionException(exception.StgException):
+    pass
+
+def print_current_patch(old_applied, new_applied):
+    def now_at(pn):
+        out.info('Now at patch "%s"' % pn)
+    if not old_applied and not new_applied:
+        pass
+    elif not old_applied:
+        now_at(new_applied[-1])
+    elif not new_applied:
+        out.info('No patch applied')
+    elif old_applied[-1] == new_applied[-1]:
+        pass
+    else:
+        now_at(new_applied[-1])
+
+class StackTransaction(object):
+    def __init__(self, stack, msg):
+        self.__stack = stack
+        self.__msg = msg
+        self.__patches = {}
+        self.__applied = list(self.__stack.patchorder.applied)
+        self.__unapplied = list(self.__stack.patchorder.unapplied)
+    def __set_patches(self, val):
+        self.__patches = dict(val)
+    patches = property(lambda self: self.__patches, __set_patches)
+    def __set_applied(self, val):
+        self.__applied = list(val)
+    applied = property(lambda self: self.__applied, __set_applied)
+    def __set_unapplied(self, val):
+        self.__unapplied = list(val)
+    unapplied = property(lambda self: self.__unapplied, __set_unapplied)
+    def __check_consistency(self):
+        remaining = set(self.__applied + self.__unapplied)
+        for pn, commit in self.__patches.iteritems():
+            if commit == None:
+                assert self.__stack.patches.exists(pn)
+            else:
+                assert pn in remaining
+    def run(self):
+        self.__check_consistency()
+
+        # Get new head commit.
+        if self.__applied:
+            top_patch = self.__applied[-1]
+            try:
+                new_head = self.__patches[top_patch]
+            except KeyError:
+                new_head = self.__stack.patches.get(top_patch).commit
+        else:
+            new_head = self.__stack.base
+
+        # Set branch head.
+        if new_head == self.__stack.head:
+            pass # same commit: OK
+        elif new_head.data.tree == self.__stack.head.data.tree:
+            pass # same tree: OK
+        else:
+            # We can't handle this case yet.
+            raise TransactionException('Error: HEAD tree changed')
+        self.__stack.set_head(new_head, self.__msg)
+
+        # Write patches.
+        for pn, commit in self.__patches.iteritems():
+            if self.__stack.patches.exists(pn):
+                p = self.__stack.patches.get(pn)
+                if commit == None:
+                    p.delete()
+                else:
+                    p.set_commit(commit, self.__msg)
+            else:
+                self.__stack.patches.new(pn, commit, self.__msg)
+        print_current_patch(self.__stack.patchorder.applied, self.__applied)
+        self.__stack.patchorder.applied = self.__applied
+        self.__stack.patchorder.unapplied = self.__unapplied
diff --git a/stgit/utils.py b/stgit/utils.py
index 3a480c0..b3f6232 100644
--- a/stgit/utils.py
+++ b/stgit/utils.py
@@ -256,3 +256,16 @@ def add_sign_line(desc, sign_str, name, email):
     if not any(s in desc for s in ['\nSigned-off-by:', '\nAcked-by:']):
         desc = desc + '\n'
     return '%s\n%s\n' % (desc, sign_str)
+
+def strip_leading(prefix, s):
+    """Strip leading prefix from a string. Blow up if the prefix isn't
+    there."""
+    assert s.startswith(prefix)
+    return s[len(prefix):]
+
+def add_dict(d1, d2):
+    """Return a new dict with the contents of both d1 and d2. In case of
+    conflicting mappings, d2 takes precedence."""
+    d = dict(d1)
+    d.update(d2)
+    return d