cmdstate: introduce a "saver" contextmanager and use it in place of save()
Previously, the state was only saved in some paths out of these functions. This
can be problematic, if the user ctrl-c's (or `kill -9`'s) the process, or we
exit out of `relocate` for anything besides the "expected" reason, we won't
record that we were in the middle of an evolve.
One of our users has discovered that this leaves hg in a weird state; the user
did something like this:
```
$ hg evolve
<something goes wrong with the merge tool, hits ctrl-c>
<deals with the merge conflicts>
$ hg evolve --continue
abort: no interrupted evolve to continue
$ hg evolve
abort: uncommitted changes
# Note: commands.status.verbose=True is set.
$ hg status
M foo
# The repository is in an unfinished *update* state.
# No unresolved merge conflicts
# To continue: hg update
```
The user did an `hg update`, but it didn't actually do anything besides take it
out of the unfinished update state (the files were still dirty in the working
directory).
====================================
Testing head checking code: Case D-1
====================================
Mercurial checks for the introduction of new heads on push. Evolution comes
into play to detect if existing branches on the server are being replaced by
some of the new one we push.
This case is part of a series of tests checking this behavior.
Category D: remote head is "obs-affected" locally, but result is not part of the push
TestCase 1: remote head is rewritten, but successors is not part of the push
.. old-state:
..
.. * 1 changeset branch
..
.. new-state:
..
.. * 1 changeset branch succeeding the old branch
.. * 1 new unrelated branch
..
.. expected-result:
..
.. * pushing only the unrelated branch: denied
..
.. graph-summary:
..
.. A ø⇠○ A'
.. |/
.. | ◔ B
.. |/
.. ●
$ . $TESTDIR/testlib/push-checkheads-util.sh
Test setup
----------
$ mkdir D1
$ cd D1
$ setuprepos
creating basic server and client repo
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd client
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mkcommit A1
created new head
$ hg debugobsolete `getid "desc(A0)" ` `getid "desc(A1)"`
1 new obsolescence markers
obsoleted 1 changesets
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mkcommit B0
created new head
$ hg log -G --hidden
@ 74ff5441d343 (draft): B0
|
| o f6082bc4ffef (draft): A1
|/
| x 8aaa48160adc (draft): A0
|/
o 1e4be0697311 (public): root
Actual testing
--------------
$ hg push -r 'desc(B0)'
pushing to $TESTTMP/D1/server (glob)
searching for changes
abort: push creates new remote head 74ff5441d343!
(merge or see 'hg help push' for details about pushing new heads)
[255]
$ cd ../..