histedit: factor most commit creation in a function

Later commits add two important items to histedit:
- Obsolescence cycle prevention
- Proper phase conservation

Those logics must be applied to all simple operations (pick, edit, mess) and
will require verbose code.

So we introduce a new function that will provide an entry point for this new.
logic.

The function build a closure to have a clear distinction between commit
arguments and data provided to the function to fulfil its logic.

hgext/histedit.py

@@ -176,6 +176,22 b' editcomment = _("""# Edit history betwee'
 #
 """)
 
+def commitfuncfor(repo, src):
+    """Build a commit function for the replacement of <src>
+
+    This function ensure we apply the same treatement to all changesets.
+
+    No such treatment is done yet.
+
+    Note that fold have its own separated logic because its handling is a bit
+    different and not easily factored out of the fold method.
+    """
+    def commitfunc(**kwargs):
+        return repo.commit(**kwargs)
+    return commitfunc
+
+
+
 def applychanges(ui, repo, ctx, opts):
     """Merge changeset from ctx (only) in the current working directory"""
     wcpar = repo.dirstate.parents()[0]
@@ -279,7 +295,8 b' def pick(ui, repo, ctx, ha, opts):'
         raise util.Abort(_('Fix up the change and run '
                            'hg histedit --continue'))
     # drop the second merge parent
-    n = repo.commit(text=oldctx.description(), user=oldctx.user(),
+    commit = commitfuncfor(repo, oldctx)
+    n = commit(text=oldctx.description(), user=oldctx.user(),
                     date=oldctx.date(), extra=oldctx.extra())
     if n is None:
         ui.warn(_('%s: empty changeset\n')
@@ -356,7 +373,8 b' def message(ui, repo, ctx, ha, opts):'
                            'hg histedit --continue'))
     message = oldctx.description() + '\n'
     message = ui.edit(message, ui.username())
-    new = repo.commit(text=message, user=oldctx.user(), date=oldctx.date(),
+    commit = commitfuncfor(repo, oldctx)
+    new = commit(text=message, user=oldctx.user(), date=oldctx.date(),
                       extra=oldctx.extra())
     newctx = repo[new]
     if oldctx.node() != newctx.node():
@@ -558,7 +576,8 b' def bootstrapcontinue(ui, repo, parentct'
             editor = cmdutil.commitforceeditor
         else:
             editor = False
-        new = repo.commit(text=message, user=ctx.user(),
+        commit = commitfuncfor(repo, ctx)
+        new = commit(text=message, user=ctx.user(),
                           date=ctx.date(), extra=ctx.extra(),
                           editor=editor)
         if new is not None: