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).
$ cat >> $HGRCPATH <<EOF
> [defaults]
> amend=-d "0 0"
> [web]
> push_ssl = false
> allow_push = *
> [phases]
> publish = False
> [alias]
> qlog = log --template='{rev} - {node|short} {desc} ({phase})\n'
> [diff]
> git = 1
> unified = 0
> [extensions]
> EOF
$ echo "evolve=$(echo $(dirname $TESTDIR))/hgext3rd/evolve/" >> $HGRCPATH
$ mkcommit() {
> echo "$1" >> "$1"
> hg add "$1"
> hg ci -m "add $1"
> }
$ hg init local
$ hg init other
$ cd local
$ touch 1 2 3 4 5 6 7 8 9 0
$ hg add 1 2 3 4 5 6 7 8 9 0
$ mkcommit A
$ mkcommit B
$ mkcommit C
$ hg log -G
@ changeset: 2:829b19580856
| tag: tip
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: add C
|
o changeset: 1:97b8f02ab29e
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: add B
|
o changeset: 0:5d8dabd3961b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add A
$ hg push ../other
pushing to ../other
searching for changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 13 changes to 13 files
$ hg -R ../other verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
checked 3 changesets with 13 changes to 13 files
$ mkcommit D
$ mkcommit E
$ hg up -q .^^
$ hg revert -r tip -a -q
$ hg ci -m 'coin' -q
$ hg log -G
@ changeset: 5:8313a6afebbb
| tag: tip
| parent: 2:829b19580856
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: coin
|
| o changeset: 4:076ec8ade1ac
| | user: test
| | date: Thu Jan 01 00:00:00 1970 +0000
| | summary: add E
| |
| o changeset: 3:824d9bb109f6
|/ user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: add D
|
o changeset: 2:829b19580856
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: add C
|
o changeset: 1:97b8f02ab29e
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: add B
|
o changeset: 0:5d8dabd3961b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add A
$ hg prune --fold -n -1 -- -2 -3
2 changesets pruned
$ hg push ../other
pushing to ../other
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 2 changes to 2 files
2 new obsolescence markers
$ hg -R ../other verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
checked 4 changesets with 15 changes to 15 files