during merge bzr twice suggest upgrade

[Alexander Belchenko]

During merge bzr twice suggest upgrade. I assume it's because during merge bzr twice open the same WT. To reproduce:

$ bzr init --knit 1
$ cd 1
$ bzr mkdir a
$ bzr ci -m 1
$ bzr branch 1 ../2
$ cd ../2
$ bzr upgrade
$ bzr mkdir b
$ bzr ci -m 2
$ cd ../1

C:\work\tmp\1>bzr merge ../2
Working tree format 3 is deprecated and a better format is available.
It is recommended that you upgrade by running the command
  bzr upgrade file:///C:/work/tmp/1/
Working tree format 3 is deprecated and a better format is available.
It is recommended that you upgrade by running the command
  bzr upgrade file:///C:/work/tmp/1/
+N b/
All changes applied successfully.

Well, we (users) are not so dumb, and we do understand suggestions at first time. It's roughly.

[Robert Collins (lifeless)]

This suggests a performance problem too, if the tree is being accessed twice.

[John A Meinel (jameinel)]

Well, it also is why OS locking is causing problems during the test suite.

Specifically, I believe "cmd_merge.run" uses a working tree to figure out what arguments mean (how they map to revisions, etc). And then it passes just the path to Merger which then re-opens the working trees.

[Aaron Bentley (abentley)]

The recent merge cleanup appears to have fixed this as a side effect. I only get the message once.