chiark - git - mdw - stgit/blob - stgit/lib/transaction.py

   1 """The L{StackTransaction} class makes it possible to make complex
   2 updates to an StGit stack in a safe and convenient way."""
   3
   4 import atexit
   5 import itertools as it
   6
   7 from stgit import exception, utils
   8 from stgit.utils import any, all
   9 from stgit.out import *
  10 from stgit.lib import git, log
  11
  12 class TransactionException(exception.StgException):
  13     """Exception raised when something goes wrong with a
  14     L{StackTransaction}."""
  15
  16 class TransactionHalted(TransactionException):
  17     """Exception raised when a L{StackTransaction} stops part-way through.
  18     Used to make a non-local jump from the transaction setup to the
  19     part of the transaction code where the transaction is run."""
  20
  21 def _print_current_patch(old_applied, new_applied):
  22     def now_at(pn):
  23         out.info('Now at patch "%s"' % pn)
  24     if not old_applied and not new_applied:
  25         pass
  26     elif not old_applied:
  27         now_at(new_applied[-1])
  28     elif not new_applied:
  29         out.info('No patch applied')
  30     elif old_applied[-1] == new_applied[-1]:
  31         pass
  32     else:
  33         now_at(new_applied[-1])
  34
  35 class _TransPatchMap(dict):
  36     """Maps patch names to sha1 strings."""
  37     def __init__(self, stack):
  38         dict.__init__(self)
  39         self.__stack = stack
  40     def __getitem__(self, pn):
  41         try:
  42             return dict.__getitem__(self, pn)
  43         except KeyError:
  44             return self.__stack.patches.get(pn).commit
  45
  46 class StackTransaction(object):
  47     """A stack transaction, used for making complex updates to an StGit
  48     stack in one single operation that will either succeed or fail
  49     cleanly.
  50
  51     The basic theory of operation is the following:
  52
  53       1. Create a transaction object.
  54
  55       2. Inside a::
  56
  57          try
  58            ...
  59          except TransactionHalted:
  60            pass
  61
  62       block, update the transaction with e.g. methods like
  63       L{pop_patches} and L{push_patch}. This may create new git
  64       objects such as commits, but will not write any refs; this means
  65       that in case of a fatal error we can just walk away, no clean-up
  66       required.
  67
  68       (Some operations may need to touch your index and working tree,
  69       though. But they are cleaned up when needed.)
  70
  71       3. After the C{try} block -- wheher or not the setup ran to
  72       completion or halted part-way through by raising a
  73       L{TransactionHalted} exception -- call the transaction's L{run}
  74       method. This will either succeed in writing the updated state to
  75       your refs and index+worktree, or fail without having done
  76       anything."""
  77     def __init__(self, stack, msg, discard_changes = False,
  78                  allow_conflicts = False):
  79         """Create a new L{StackTransaction}.
  80
  81         @param discard_changes: Discard any changes in index+worktree
  82         @type discard_changes: bool
  83         @param allow_conflicts: Whether to allow pre-existing conflicts
  84         @type allow_conflicts: bool or function of L{StackTransaction}"""
  85         self.__stack = stack
  86         self.__msg = msg
  87         self.__patches = _TransPatchMap(stack)
  88         self.__applied = list(self.__stack.patchorder.applied)
  89         self.__unapplied = list(self.__stack.patchorder.unapplied)
  90         self.__hidden = list(self.__stack.patchorder.hidden)
  91         self.__conflicting_push = None
  92         self.__error = None
  93         self.__current_tree = self.__stack.head.data.tree
  94         self.__base = self.__stack.base
  95         self.__discard_changes = discard_changes
  96         self.__bad_head = None
  97         if isinstance(allow_conflicts, bool):
  98             self.__allow_conflicts = lambda trans: allow_conflicts
  99         else:
 100             self.__allow_conflicts = allow_conflicts
 101         self.__temp_index = self.temp_index_tree = None
 102     stack = property(lambda self: self.__stack)
 103     patches = property(lambda self: self.__patches)
 104     def __set_applied(self, val):
 105         self.__applied = list(val)
 106     applied = property(lambda self: self.__applied, __set_applied)
 107     def __set_unapplied(self, val):
 108         self.__unapplied = list(val)
 109     unapplied = property(lambda self: self.__unapplied, __set_unapplied)
 110     def __set_hidden(self, val):
 111         self.__hidden = list(val)
 112     hidden = property(lambda self: self.__hidden, __set_hidden)
 113     all_patches = property(lambda self: (self.__applied + self.__unapplied
 114                                          + self.__hidden))
 115     def __set_base(self, val):
 116         assert (not self.__applied
 117                 or self.patches[self.applied[0]].data.parent == val)
 118         self.__base = val
 119     base = property(lambda self: self.__base, __set_base)
 120     @property
 121     def temp_index(self):
 122         if not self.__temp_index:
 123             self.__temp_index = self.__stack.repository.temp_index()
 124             atexit.register(self.__temp_index.delete)
 125         return self.__temp_index
 126     @property
 127     def top(self):
 128         if self.__applied:
 129             return self.__patches[self.__applied[-1]]
 130         else:
 131             return self.__base
 132     def __get_head(self):
 133         if self.__bad_head:
 134             return self.__bad_head
 135         else:
 136             return self.top
 137     def __set_head(self, val):
 138         self.__bad_head = val
 139     head = property(__get_head, __set_head)
 140     def __checkout(self, tree, iw, allow_bad_head):
 141         if not (allow_bad_head or self.__stack.head_top_equal()):
 142             out.error(
 143                 'HEAD and top are not the same.',
 144                 'This can happen if you modify a branch with git.',
 145                 '"stg repair --help" explains more about what to do next.')
 146             self.__abort()
 147         if self.__current_tree == tree and not self.__discard_changes:
 148             # No tree change, but we still want to make sure that
 149             # there are no unresolved conflicts. Conflicts
 150             # conceptually "belong" to the topmost patch, and just
 151             # carrying them along to another patch is confusing.
 152             if (self.__allow_conflicts(self) or iw == None
 153                 or not iw.index.conflicts()):
 154                 return
 155             out.error('Need to resolve conflicts first')
 156             self.__abort()
 157         assert iw != None
 158         if self.__discard_changes:
 159             iw.checkout_hard(tree)
 160         else:
 161             iw.checkout(self.__current_tree, tree)
 162         self.__current_tree = tree
 163     @staticmethod
 164     def __abort():
 165         raise TransactionException(
 166             'Command aborted (all changes rolled back)')
 167     def __check_consistency(self):
 168         remaining = set(self.all_patches)
 169         for pn, commit in self.__patches.iteritems():
 170             if commit == None:
 171                 assert self.__stack.patches.exists(pn)
 172             else:
 173                 assert pn in remaining
 174     def abort(self, iw = None):
 175         # The only state we need to restore is index+worktree.
 176         if iw:
 177             self.__checkout(self.__stack.head.data.tree, iw,
 178                             allow_bad_head = True)
 179     def run(self, iw = None, set_head = True, allow_bad_head = False):
 180         """Execute the transaction. Will either succeed, or fail (with an
 181         exception) and do nothing."""
 182         self.__check_consistency()
 183         log.log_external_mods(self.__stack)
 184         new_head = self.head
 185
 186         # Set branch head.
 187         if set_head:
 188             if iw:
 189                 try:
 190                     self.__checkout(new_head.data.tree, iw, allow_bad_head)
 191                 except git.CheckoutException:
 192                     # We have to abort the transaction.
 193                     self.abort(iw)
 194                     self.__abort()
 195             self.__stack.set_head(new_head, self.__msg)
 196
 197         if self.__error:
 198             out.error(self.__error)
 199
 200         # Write patches.
 201         def write(msg):
 202             for pn, commit in self.__patches.iteritems():
 203                 if self.__stack.patches.exists(pn):
 204                     p = self.__stack.patches.get(pn)
 205                     if commit == None:
 206                         p.delete()
 207                     else:
 208                         p.set_commit(commit, msg)
 209                 else:
 210                     self.__stack.patches.new(pn, commit, msg)
 211             self.__stack.patchorder.applied = self.__applied
 212             self.__stack.patchorder.unapplied = self.__unapplied
 213             self.__stack.patchorder.hidden = self.__hidden
 214             log.log_entry(self.__stack, msg)
 215         old_applied = self.__stack.patchorder.applied
 216         write(self.__msg)
 217         if self.__conflicting_push != None:
 218             self.__patches = _TransPatchMap(self.__stack)
 219             self.__conflicting_push()
 220             write(self.__msg + ' (CONFLICT)')
 221         _print_current_patch(old_applied, self.__applied)
 222
 223         if self.__error:
 224             return utils.STGIT_CONFLICT
 225         else:
 226             return utils.STGIT_SUCCESS
 227
 228     def __halt(self, msg):
 229         self.__error = msg
 230         raise TransactionHalted(msg)
 231
 232     @staticmethod
 233     def __print_popped(popped):
 234         if len(popped) == 0:
 235             pass
 236         elif len(popped) == 1:
 237             out.info('Popped %s' % popped[0])
 238         else:
 239             out.info('Popped %s -- %s' % (popped[-1], popped[0]))
 240
 241     def pop_patches(self, p):
 242         """Pop all patches pn for which p(pn) is true. Return the list of
 243         other patches that had to be popped to accomplish this. Always
 244         succeeds."""
 245         popped = []
 246         for i in xrange(len(self.applied)):
 247             if p(self.applied[i]):
 248                 popped = self.applied[i:]
 249                 del self.applied[i:]
 250                 break
 251         popped1 = [pn for pn in popped if not p(pn)]
 252         popped2 = [pn for pn in popped if p(pn)]
 253         self.unapplied = popped1 + popped2 + self.unapplied
 254         self.__print_popped(popped)
 255         return popped1
 256
 257     def delete_patches(self, p):
 258         """Delete all patches pn for which p(pn) is true. Return the list of
 259         other patches that had to be popped to accomplish this. Always
 260         succeeds."""
 261         popped = []
 262         all_patches = self.applied + self.unapplied + self.hidden
 263         for i in xrange(len(self.applied)):
 264             if p(self.applied[i]):
 265                 popped = self.applied[i:]
 266                 del self.applied[i:]
 267                 break
 268         popped = [pn for pn in popped if not p(pn)]
 269         self.unapplied = popped + [pn for pn in self.unapplied if not p(pn)]
 270         self.hidden = [pn for pn in self.hidden if not p(pn)]
 271         self.__print_popped(popped)
 272         for pn in all_patches:
 273             if p(pn):
 274                 s = ['', ' (empty)'][self.patches[pn].data.is_nochange()]
 275                 self.patches[pn] = None
 276                 out.info('Deleted %s%s' % (pn, s))
 277         return popped
 278
 279     def push_patch(self, pn, iw = None):
 280         """Attempt to push the named patch. If this results in conflicts,
 281         halts the transaction. If index+worktree are given, spill any
 282         conflicts to them."""
 283         orig_cd = self.patches[pn].data
 284         cd = orig_cd.set_committer(None)
 285         s = ['', ' (empty)'][cd.is_nochange()]
 286         oldparent = cd.parent
 287         cd = cd.set_parent(self.top)
 288         base = oldparent.data.tree
 289         ours = cd.parent.data.tree
 290         theirs = cd.tree
 291         tree, self.temp_index_tree = self.temp_index.merge(
 292             base, ours, theirs, self.temp_index_tree)
 293         merge_conflict = False
 294         if not tree:
 295             if iw == None:
 296                 self.__halt('%s does not apply cleanly' % pn)
 297             try:
 298                 self.__checkout(ours, iw, allow_bad_head = False)
 299             except git.CheckoutException:
 300                 self.__halt('Index/worktree dirty')
 301             try:
 302                 iw.merge(base, ours, theirs)
 303                 tree = iw.index.write_tree()
 304                 self.__current_tree = tree
 305                 s = ' (modified)'
 306             except git.MergeConflictException:
 307                 tree = ours
 308                 merge_conflict = True
 309                 s = ' (conflict)'
 310             except git.MergeException, e:
 311                 self.__halt(str(e))
 312         cd = cd.set_tree(tree)
 313         if any(getattr(cd, a) != getattr(orig_cd, a) for a in
 314                ['parent', 'tree', 'author', 'message']):
 315             comm = self.__stack.repository.commit(cd)
 316         else:
 317             comm = None
 318             s = ' (unmodified)'
 319         out.info('Pushed %s%s' % (pn, s))
 320         def update():
 321             if comm:
 322                 self.patches[pn] = comm
 323             if pn in self.hidden:
 324                 x = self.hidden
 325             else:
 326                 x = self.unapplied
 327             del x[x.index(pn)]
 328             self.applied.append(pn)
 329         if merge_conflict:
 330             # We've just caused conflicts, so we must allow them in
 331             # the final checkout.
 332             self.__allow_conflicts = lambda trans: True
 333
 334             # Save this update so that we can run it a little later.
 335             self.__conflicting_push = update
 336             self.__halt('Merge conflict')
 337         else:
 338             # Update immediately.
 339             update()
 340
 341     def reorder_patches(self, applied, unapplied, hidden, iw = None):
 342         """Push and pop patches to attain the given ordering."""
 343         common = len(list(it.takewhile(lambda (a, b): a == b,
 344                                        zip(self.applied, applied))))
 345         to_pop = set(self.applied[common:])
 346         self.pop_patches(lambda pn: pn in to_pop)
 347         for pn in applied[common:]:
 348             self.push_patch(pn, iw)
 349         assert self.applied == applied
 350         assert set(self.unapplied + self.hidden) == set(unapplied + hidden)
 351         self.unapplied = unapplied
 352         self.hidden = hidden