Switch --store
==============

In workflows that a single working tree, like co-located branches, sometimes
you want to switch while you have uncommitted changes.  By default, ``switch``
will apply your uncommitted changes to the new branch that you switch to.  But
often you don't want that.  You just want to do some work in the other branch,
and eventually return to this branch and work some more.

You could run ``brz shelve --all`` before switching, to store the changes
safely.  So you have to know that there are uncommitted changes present, and
you have to remember to run ``brz shelve --all``.  Then when you switch back to
the branch, you need to remember to unshelve the changes, and you need to know
what their shelf-id was.

Using ``switch --store`` takes care of all of this for you.  If there are any
uncommitted changes in your tree, it stores them in your branch.  It then
restores any uncommitted changes that were stored in the branch of your target
tree.  It's almost like having two working trees and using ``cd`` to switch
between them.

To take an example, first we'd set up a co-located branch::

  $ brz init foo
  Created a standalone tree (format: 2a)
  $ cd foo
  $ brz switch -b foo

Now create committed and uncommitted changes::

  $ touch committed
  $ brz add
  adding committed
  $ brz commit -m "Add committed"
  Committing to: /home/abentley/sandbox/foo/
  added committed
  Committed revision 1.
  $ touch uncommitted
  $ brz add
  adding uncommitted
  $ ls
  committed  uncommitted

Now create a new branch using ``--store``.  The uncommitted changes are stored
in "foo", but the committed changes are retained.
::

  $ brz switch -b --store bar
  Uncommitted changes stored in branch "foo".
  Tree is up to date at revision 1.
  Switched to branch: /home/abentley/sandbox/foo/
  abentley@speedy:~/sandbox/foo$ ls
  committed

Now, create uncommitted changes in "bar"::

  $ touch uncommitted-bar
  $ brz add
  adding uncommitted-bar

Finally, switch back to "foo"::

  $ brz switch --store foo
  Uncommitted changes stored in branch "bar".
  Tree is up to date at revision 1.
  Switched to branch: /home/abentley/sandbox/foo/
  $ ls
  committed  uncommitted

Each branch holds only one set of stored changes.  If you try to store a second
set, you get an error.  If you use ``--store`` all the time, this can't happen.
But if you use plain switch, then it won't restore the uncommitted changes
already present::

  $ brz switch bar
  Tree is up to date at revision 1.
  Switched to branch: /home/abentley/sandbox/foo/
  $ brz switch --store foo
  brz: ERROR: Cannot store uncommitted changes because this branch already
  stores uncommitted changes.

If you're working in a branch that already has stored changes, you can restore
them with ``brz switch . --store``::

  $ brz shelve --all -m "Uncommitted changes from foo"
  Selected changes:
  -D  uncommitted
  Changes shelved with id "1".
  $ brz switch . --store
  Tree is up to date at revision 1.
  Switched to branch: /home/abentley/sandbox/foo/
  $ ls
  committed  uncommitted-bar
