histedit: switch state to store node instead of ctx

Currently, if the node no longer exists, the state object fails to load
and pukes with an exception. Changing the state object to only store the
node allows callers to handle these cases.  For instance, in
bootstrapcontinue we can now detect that the node doesn't exist and exit
gracefully.

The alternative is to have the state object store something like None
when the node doesn't exist, but then outside callers won't be able to
access the old node for recovery (unless we store both the node and the
ctx, but why bother).

More importantly it allows us to detect this case when doing hg histedit
--abort.  Currently this situation results in both --continue and
--abort being broken and the user has to rm .hg/histedit-state to unwedge
their repo.
(description by Durham Goode)

hgext/histedit.py

@@ -190,13 +190,13 b' editcomment = _("""# Edit history betwee'
 """)
 
 class histeditstate(object):
-    def __init__(self, repo, parentctx=None, rules=None, keep=None,
+    def __init__(self, repo, parentctxnode=None, rules=None, keep=None,
             topmost=None, replacements=None, lock=None, wlock=None):
         self.repo = repo
         self.rules = rules
         self.keep = keep
         self.topmost = topmost
-        self.parentctx = parentctx
+        self.parentctxnode = parentctxnode
         self.lock = lock
         self.wlock = wlock
         if replacements is None:
@@ -215,7 +215,7 b' class histeditstate(object):'
 
         parentctxnode, rules, keep, topmost, replacements = pickle.load(fp)
 
-        self.parentctx = self.repo[parentctxnode]
+        self.parentctxnode = parentctxnode
         self.rules = rules
         self.keep = keep
         self.topmost = topmost
@@ -223,7 +223,7 b' class histeditstate(object):'
 
     def write(self):
         fp = self.repo.vfs('histedit-state', 'w')
-        pickle.dump((self.parentctx.node(), self.rules, self.keep,
+        pickle.dump((self.parentctxnode, self.rules, self.keep,
                      self.topmost, self.replacements), fp)
         fp.close()
 
@@ -347,7 +347,8 b' def collapse(repo, first, last, commitop'
     return repo.commitctx(new)
 
 def pick(ui, state, ha, opts):
-    repo, ctx = state.repo, state.parentctx
+    repo, ctxnode = state.repo, state.parentctxnode
+    ctx = repo[ctxnode]
     oldctx = repo[ha]
     if oldctx.parents()[0] == ctx:
         ui.debug('node %s unchanged\n' % ha[:12])
@@ -369,7 +370,8 b' def pick(ui, state, ha, opts):'
 
 
 def edit(ui, state, ha, opts):
-    repo, ctx = state.repo, state.parentctx
+    repo, ctxnode = state.repo, state.parentctxnode
+    ctx = repo[ctxnode]
     oldctx = repo[ha]
     hg.update(repo, ctx.node())
     applychanges(ui, repo, oldctx, opts)
@@ -383,7 +385,8 b' def rollup(ui, state, ha, opts):'
     return fold(ui, state, ha, rollupopts)
 
 def fold(ui, state, ha, opts):
-    repo, ctx = state.repo, state.parentctx
+    repo, ctxnode = state.repo, state.parentctxnode
+    ctx = repo[ctxnode]
     oldctx = repo[ha]
     hg.update(repo, ctx.node())
     stats = applychanges(ui, repo, oldctx, opts)
@@ -439,12 +442,14 b' def finishfold(ui, repo, ctx, oldctx, ne'
     return repo[n], replacements
 
 def drop(ui, state, ha, opts):
-    repo, ctx = state.repo, state.parentctx
+    repo, ctxnode = state.repo, state.parentctxnode
+    ctx = repo[ctxnode]
     return ctx, [(repo[ha].node(), ())]
 
 
 def message(ui, state, ha, opts):
-    repo, ctx = state.repo, state.parentctx
+    repo, ctxnode = state.repo, state.parentctxnode
+    ctx = repo[ctxnode]
     oldctx = repo[ha]
     hg.update(repo, ctx.node())
     stats = applychanges(ui, repo, oldctx, opts)
@@ -604,7 +609,7 b' def _histedit(ui, repo, state, *freeargs'
         ui.debug('restore wc to old parent %s\n' % node.short(state.topmost))
         # check whether we should update away
         parentnodes = [c.node() for c in repo[None].parents()]
-        for n in leafs | set([state.parentctx.node()]):
+        for n in leafs | set([state.parentctxnode]):
             if n in parentnodes:
                 hg.clean(repo, state.topmost)
                 break
@@ -660,9 +665,9 b' def _histedit(ui, repo, state, *freeargs'
                  if l and not l.startswith('#')]
         rules = verifyrules(rules, repo, ctxs)
 
-        parentctx = repo[root].parents()[0]
+        parentctxnode = repo[root].parents()[0].node()
 
-        state.parentctx = parentctx
+        state.parentctxnode = parentctxnode
         state.rules = rules
         state.keep = keep
         state.topmost = topmost
@@ -673,11 +678,12 b' def _histedit(ui, repo, state, *freeargs'
         action, ha = state.rules.pop(0)
         ui.debug('histedit: processing %s %s\n' % (action, ha[:12]))
         actfunc = actiontable[action]
-        state.parentctx, replacement_ = actfunc(ui, state, ha, opts)
+        parentctx, replacement_ = actfunc(ui, state, ha, opts)
+        state.parentctxnode = parentctx.node()
         state.replacements.extend(replacement_)
     state.write()
 
-    hg.update(repo, state.parentctx.node())
+    hg.update(repo, state.parentctxnode)
 
     mapping, tmpnodes, created, ntm = processreplacement(state)
     if mapping:
@@ -730,7 +736,8 b' def gatherchildren(repo, ctx):'
     return newchildren
 
 def bootstrapcontinue(ui, state, opts):
-    repo, parentctx = state.repo, state.parentctx
+    repo, parentctxnode = state.repo, state.parentctxnode
+    parentctx = repo[parentctxnode]
     action, currentnode = state.rules.pop(0)
     ctx = repo[currentnode]
 
@@ -786,7 +793,7 b' def bootstrapcontinue(ui, state, opts):'
         # otherwise update "parentctx" before proceeding to further operation
         parentctx = repo[newchildren[-1]]
 
-    state.parentctx = parentctx
+    state.parentctxnode = parentctx.node()
     state.replacements.extend(replacements)
 
     return state