evolvestate: add a class to wrap the state of `hg evolve` command
This patch adds a new file which contains a class which will act as a wrapper
for the data to be stored or used during the `hg evolve` command. This patch
just introduces the file and does not use it at the moment. The upcoming patches
will start using it.
testing topic with shelve extension
------------------------------------
$ . "$TESTDIR/testlib/topic_setup.sh"
$ hg init repo
$ cd repo
$ cat <<EOF >>.hg/hgrc
> [extensions]
> shelve=
> EOF
$ touch a
$ echo "Hello" >> a
$ hg topic "testing-shelve"
marked working directory as topic: testing-shelve
$ hg topic
* testing-shelve (0 changesets)
$ hg ci -m "First commit" -A
adding a
active topic 'testing-shelve' grew its first changeset
$ hg topic
* testing-shelve (1 changesets)
$ echo " World" >> a
$ hg stack
### topic: testing-shelve
### target: default (branch)
t1@ First commit (current)
shelve test
-----------
$ hg shelve
shelved as default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg topic
* testing-shelve (1 changesets)
$ hg stack
### topic: testing-shelve
### target: default (branch)
t1@ First commit (current)
unshelve test
-------------
$ hg unshelve
unshelving change 'default'
$ hg topic
* testing-shelve (1 changesets)
$ hg stack
### topic: testing-shelve
### target: default (branch)
t1@ First commit (current)