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).
Orphan changeset and trying to relocate a node on top of itself (issue6097)
https://bz.mercurial-scm.org/show_bug.cgi?id=6097
$ . $TESTDIR/testlib/common.sh
$ cat << EOF >> $HGRCPATH
> [extensions]
> rebase =
> evolve =
> EOF
$ hg init issue6097
$ cd issue6097
$ echo apricot > a
$ hg ci -qAm apricot
$ echo banana > b
$ hg ci -qAm banana
Let's go back to amend 0 and make an orphan out of 1
$ hg up -q 0
$ echo coconut > c
$ hg add -q c
$ hg ci --amend -m 'apricot and coconut'
1 new orphan changesets
Now rebase the successor of 0 on top of 1
$ hg rebase -r . -d 1
rebasing 2:32acf8fb1b23 "apricot and coconut" (tip)
1 new orphan changesets
Pruning 1 just to get it out of the way
$ hg prune -q 1
Note how both the regular DAG and the obsolescence graph are linear, but the
paths from 3 to 0 are different: 3-1-0 and 3-2-0
$ hg log -G
@ changeset: 3:2868fe6df617
| tag: tip
| parent: 1:e0486f65907d
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| instability: orphan
| summary: apricot and coconut
|
x changeset: 1:e0486f65907d
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| obsolete: pruned using prune
| summary: banana
|
x changeset: 0:692cc7b6212c
user: test
date: Thu Jan 01 00:00:00 1970 +0000
obsolete: rewritten using amend, rebase as 3:2868fe6df617
summary: apricot
$ hg obslog
@ 2868fe6df617 (3) apricot and coconut
|
x 32acf8fb1b23 (2) apricot and coconut
| rewritten(parent, content) as 2868fe6df617 using rebase by test (Thu Jan 01 00:00:00 1970 +0000)
|
x 692cc7b6212c (0) apricot
rewritten(description, content) as 32acf8fb1b23 using amend by test (Thu Jan 01 00:00:00 1970 +0000)
$ hg evolve -r .
move:[3] apricot and coconut
atop:[-1]
working directory is now at bb847d1d3a5f
$ hg log -G
@ changeset: 4:bb847d1d3a5f
tag: tip
parent: -1:000000000000
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: apricot and coconut
$ hg obslog
@ bb847d1d3a5f (4) apricot and coconut
|
x 2868fe6df617 (3) apricot and coconut
| rewritten(parent) as bb847d1d3a5f using evolve by test (Thu Jan 01 00:00:00 1970 +0000)
|
x 32acf8fb1b23 (2) apricot and coconut
| rewritten(parent, content) as 2868fe6df617 using rebase by test (Thu Jan 01 00:00:00 1970 +0000)
|
x 692cc7b6212c (0) apricot
rewritten(description, content) as 32acf8fb1b23 using amend by test (Thu Jan 01 00:00:00 1970 +0000)