shelve: move rebasing logic to a separate function

shelve: move rebasing logic to a separate function

Rebasing restored shelved commit onto the right destination is done
differently in traditional and obs-based unshelve:
- for traditional, we just rebase it
- for obs-based, we need to check whether a successor of
  the restored commit already exists in the destination (this
  might happen when unshelving twice on the same destination)
This is the reason why this piece of logic should be in its own
function: to not have excessive complexity in the main function.

--- a/hgext/shelve.py	Thu Nov 10 10:51:06 2016 -0800
+++ b/hgext/shelve.py	Thu Nov 10 10:57:10 2016 -0800
@@ -658,6 +658,44 @@
     ui.quiet = oldquiet
     return repo, shelvectx
 
+def _rebaserestoredcommit(ui, repo, opts, tr, oldtiprev, basename, pctx,
+                          tmpwctx, shelvectx, branchtorestore):
+    """Rebase restored commit from its original location to a destination"""
+    # If the shelve is not immediately on top of the commit
+    # we'll be merging with, rebase it to be on top.
+    if tmpwctx.node() == shelvectx.parents()[0].node():
+        return shelvectx
+
+    ui.status(_('rebasing shelved changes\n'))
+    try:
+        rebase.rebase(ui, repo, **{
+            'rev': [shelvectx.rev()],
+            'dest': str(tmpwctx.rev()),
+            'keep': True,
+            'tool': opts.get('tool', ''),
+        })
+    except error.InterventionRequired:
+        tr.close()
+
+        stripnodes = [repo.changelog.node(rev)
+                      for rev in xrange(oldtiprev, len(repo))]
+        shelvedstate.save(repo, basename, pctx, tmpwctx, stripnodes,
+                          branchtorestore)
+
+        util.rename(repo.join('rebasestate'),
+                    repo.join('unshelverebasestate'))
+        raise error.InterventionRequired(
+            _("unresolved conflicts (see 'hg resolve', then "
+              "'hg unshelve --continue')"))
+
+    # refresh ctx after rebase completes
+    shelvectx = repo['tip']
+
+    if not shelvectx in tmpwctx.children():
+        # rebase was a no-op, so it produced no child commit
+        shelvectx = tmpwctx
+    return shelvectx
+
 @command('unshelve',
          [('a', 'abort', None,
            _('abort an incomplete unshelve operation')),
@@ -789,38 +827,9 @@
         if shelvectx.branch() != shelvectx.p1().branch():
             branchtorestore = shelvectx.branch()
 
-        # If the shelve is not immediately on top of the commit
-        # we'll be merging with, rebase it to be on top.
-        if tmpwctx.node() != shelvectx.parents()[0].node():
-            ui.status(_('rebasing shelved changes\n'))
-            try:
-                rebase.rebase(ui, repo, **{
-                    'rev' : [shelvectx.rev()],
-                    'dest' : str(tmpwctx.rev()),
-                    'keep' : True,
-                    'tool' : opts.get('tool', ''),
-                })
-            except error.InterventionRequired:
-                tr.close()
-
-                stripnodes = [repo.changelog.node(rev)
-                              for rev in xrange(oldtiprev, len(repo))]
-                shelvedstate.save(repo, basename, pctx, tmpwctx, stripnodes,
-                                  branchtorestore)
-
-                util.rename(repo.join('rebasestate'),
-                            repo.join('unshelverebasestate'))
-                raise error.InterventionRequired(
-                    _("unresolved conflicts (see 'hg resolve', then "
-                      "'hg unshelve --continue')"))
-
-            # refresh ctx after rebase completes
-            shelvectx = repo['tip']
-
-            if not shelvectx in tmpwctx.children():
-                # rebase was a no-op, so it produced no child commit
-                shelvectx = tmpwctx
-
+        shelvectx = _rebaserestoredcommit(ui, repo, opts, tr, oldtiprev,
+                                          basename, pctx, tmpwctx, shelvectx,
+                                          branchtorestore)
         mergefiles(ui, repo, pctx, shelvectx)
         restorebranch(ui, repo, branchtorestore)