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
  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, allow_conflicts = False):
  78         self.__stack = stack
  79         self.__msg = msg
  80         self.__patches = _TransPatchMap(stack)
  81         self.__applied = list(self.__stack.patchorder.applied)
  82         self.__unapplied = list(self.__stack.patchorder.unapplied)
  83         self.__hidden = list(self.__stack.patchorder.hidden)
  84         self.__error = None
  85         self.__current_tree = self.__stack.head.data.tree
  86         self.__base = self.__stack.base
  87         if isinstance(allow_conflicts, bool):
  88             self.__allow_conflicts = lambda trans: allow_conflicts
  89         else:
  90             self.__allow_conflicts = allow_conflicts
  91         self.__temp_index = self.temp_index_tree = None
  92     stack = property(lambda self: self.__stack)
  93     patches = property(lambda self: self.__patches)
  94     def __set_applied(self, val):
  95         self.__applied = list(val)
  96     applied = property(lambda self: self.__applied, __set_applied)
  97     def __set_unapplied(self, val):
  98         self.__unapplied = list(val)
  99     unapplied = property(lambda self: self.__unapplied, __set_unapplied)
 100     def __set_hidden(self, val):
 101         self.__hidden = list(val)
 102     hidden = property(lambda self: self.__hidden, __set_hidden)
 103     def __set_base(self, val):
 104         assert (not self.__applied
 105                 or self.patches[self.applied[0]].data.parent == val)
 106         self.__base = val
 107     base = property(lambda self: self.__base, __set_base)
 108     @property
 109     def temp_index(self):
 110         if not self.__temp_index:
 111             self.__temp_index = self.__stack.repository.temp_index()
 112             atexit.register(self.__temp_index.delete)
 113         return self.__temp_index
 114     def __checkout(self, tree, iw):
 115         if not self.__stack.head_top_equal():
 116             out.error(
 117                 'HEAD and top are not the same.',
 118                 'This can happen if you modify a branch with git.',
 119                 '"stg repair --help" explains more about what to do next.')
 120             self.__abort()
 121         if self.__current_tree == tree:
 122             # No tree change, but we still want to make sure that
 123             # there are no unresolved conflicts. Conflicts
 124             # conceptually "belong" to the topmost patch, and just
 125             # carrying them along to another patch is confusing.
 126             if (self.__allow_conflicts(self) or iw == None
 127                 or not iw.index.conflicts()):
 128                 return
 129             out.error('Need to resolve conflicts first')
 130             self.__abort()
 131         assert iw != None
 132         iw.checkout(self.__current_tree, tree)
 133         self.__current_tree = tree
 134     @staticmethod
 135     def __abort():
 136         raise TransactionException(
 137             'Command aborted (all changes rolled back)')
 138     def __check_consistency(self):
 139         remaining = set(self.__applied + self.__unapplied + self.__hidden)
 140         for pn, commit in self.__patches.iteritems():
 141             if commit == None:
 142                 assert self.__stack.patches.exists(pn)
 143             else:
 144                 assert pn in remaining
 145     @property
 146     def __head(self):
 147         if self.__applied:
 148             return self.__patches[self.__applied[-1]]
 149         else:
 150             return self.__base
 151     def abort(self, iw = None):
 152         # The only state we need to restore is index+worktree.
 153         if iw:
 154             self.__checkout(self.__stack.head.data.tree, iw)
 155     def run(self, iw = None, set_head = True):
 156         """Execute the transaction. Will either succeed, or fail (with an
 157         exception) and do nothing."""
 158         self.__check_consistency()
 159         new_head = self.__head
 160
 161         # Set branch head.
 162         if set_head:
 163             if iw:
 164                 try:
 165                     self.__checkout(new_head.data.tree, iw)
 166                 except git.CheckoutException:
 167                     # We have to abort the transaction.
 168                     self.abort(iw)
 169                     self.__abort()
 170             self.__stack.set_head(new_head, self.__msg)
 171
 172         if self.__error:
 173             out.error(self.__error)
 174
 175         # Write patches.
 176         for pn, commit in self.__patches.iteritems():
 177             if self.__stack.patches.exists(pn):
 178                 p = self.__stack.patches.get(pn)
 179                 if commit == None:
 180                     p.delete()
 181                 else:
 182                     p.set_commit(commit, self.__msg)
 183             else:
 184                 self.__stack.patches.new(pn, commit, self.__msg)
 185         _print_current_patch(self.__stack.patchorder.applied, self.__applied)
 186         self.__stack.patchorder.applied = self.__applied
 187         self.__stack.patchorder.unapplied = self.__unapplied
 188         self.__stack.patchorder.hidden = self.__hidden
 189
 190         if self.__error:
 191             return utils.STGIT_CONFLICT
 192         else:
 193             return utils.STGIT_SUCCESS
 194
 195     def __halt(self, msg):
 196         self.__error = msg
 197         raise TransactionHalted(msg)
 198
 199     @staticmethod
 200     def __print_popped(popped):
 201         if len(popped) == 0:
 202             pass
 203         elif len(popped) == 1:
 204             out.info('Popped %s' % popped[0])
 205         else:
 206             out.info('Popped %s -- %s' % (popped[-1], popped[0]))
 207
 208     def pop_patches(self, p):
 209         """Pop all patches pn for which p(pn) is true. Return the list of
 210         other patches that had to be popped to accomplish this. Always
 211         succeeds."""
 212         popped = []
 213         for i in xrange(len(self.applied)):
 214             if p(self.applied[i]):
 215                 popped = self.applied[i:]
 216                 del self.applied[i:]
 217                 break
 218         popped1 = [pn for pn in popped if not p(pn)]
 219         popped2 = [pn for pn in popped if p(pn)]
 220         self.unapplied = popped1 + popped2 + self.unapplied
 221         self.__print_popped(popped)
 222         return popped1
 223
 224     def delete_patches(self, p):
 225         """Delete all patches pn for which p(pn) is true. Return the list of
 226         other patches that had to be popped to accomplish this. Always
 227         succeeds."""
 228         popped = []
 229         all_patches = self.applied + self.unapplied + self.hidden
 230         for i in xrange(len(self.applied)):
 231             if p(self.applied[i]):
 232                 popped = self.applied[i:]
 233                 del self.applied[i:]
 234                 break
 235         popped = [pn for pn in popped if not p(pn)]
 236         self.unapplied = popped + [pn for pn in self.unapplied if not p(pn)]
 237         self.hidden = [pn for pn in self.hidden if not p(pn)]
 238         self.__print_popped(popped)
 239         for pn in all_patches:
 240             if p(pn):
 241                 s = ['', ' (empty)'][self.patches[pn].data.is_nochange()]
 242                 self.patches[pn] = None
 243                 out.info('Deleted %s%s' % (pn, s))
 244         return popped
 245
 246     def push_patch(self, pn, iw = None):
 247         """Attempt to push the named patch. If this results in conflicts,
 248         halts the transaction. If index+worktree are given, spill any
 249         conflicts to them."""
 250         orig_cd = self.patches[pn].data
 251         cd = orig_cd.set_committer(None)
 252         s = ['', ' (empty)'][cd.is_nochange()]
 253         oldparent = cd.parent
 254         cd = cd.set_parent(self.__head)
 255         base = oldparent.data.tree
 256         ours = cd.parent.data.tree
 257         theirs = cd.tree
 258         tree, self.temp_index_tree = self.temp_index.merge(
 259             base, ours, theirs, self.temp_index_tree)
 260         merge_conflict = False
 261         if not tree:
 262             if iw == None:
 263                 self.__halt('%s does not apply cleanly' % pn)
 264             try:
 265                 self.__checkout(ours, iw)
 266             except git.CheckoutException:
 267                 self.__halt('Index/worktree dirty')
 268             try:
 269                 iw.merge(base, ours, theirs)
 270                 tree = iw.index.write_tree()
 271                 self.__current_tree = tree
 272                 s = ' (modified)'
 273             except git.MergeConflictException:
 274                 tree = ours
 275                 merge_conflict = True
 276                 s = ' (conflict)'
 277             except git.MergeException, e:
 278                 self.__halt(str(e))
 279         cd = cd.set_tree(tree)
 280         if any(getattr(cd, a) != getattr(orig_cd, a) for a in
 281                ['parent', 'tree', 'author', 'message']):
 282             self.patches[pn] = self.__stack.repository.commit(cd)
 283         else:
 284             s = ' (unmodified)'
 285         if pn in self.hidden:
 286             x = self.hidden
 287         else:
 288             x = self.unapplied
 289         del x[x.index(pn)]
 290         self.applied.append(pn)
 291         out.info('Pushed %s%s' % (pn, s))
 292         if merge_conflict:
 293             # We've just caused conflicts, so we must allow them in
 294             # the final checkout.
 295             self.__allow_conflicts = lambda trans: True
 296
 297             self.__halt('Merge conflict')
 298
 299     def reorder_patches(self, applied, unapplied, hidden, iw = None):
 300         """Push and pop patches to attain the given ordering."""
 301         common = len(list(it.takewhile(lambda (a, b): a == b,
 302                                        zip(self.applied, applied))))
 303         to_pop = set(self.applied[common:])
 304         self.pop_patches(lambda pn: pn in to_pop)
 305         for pn in applied[common:]:
 306             self.push_patch(pn, iw)
 307         assert self.applied == applied
 308         assert set(self.unapplied + self.hidden) == set(unapplied + hidden)
 309         self.unapplied = unapplied
 310         self.hidden = hidden