localrepo: stop doing special dirstate backup at transaction open
Since the dirstate writes are already managed by the transaction, we already do
a backup of the dirstate when necessary (and even trigger one to keep `hg
rollback` happy).
We needs some special code to deal with the initial empty checkout, but it is
not too complicated.
Managing variable filename (as dirstate-v2 uses) at the "journalfile" level, is
complex and fragile (which is consistent with the fact these files are not
journal…). If we no longer do it, our life is significantly simpler.
In some sense, we apply the xkcd-1134¹ solution to our savebackup/restorebackup
problem.
[1] https://xkcd.com/1134/
(the change to test-hardlink are expect as decreasing the number of duplicated
backup drive the hardlink count down)
$ cat << EOF >> $HGRCPATH
> [extensions]
> rebase=
> [alias]
> tglog = log -G -T "{rev} '{desc}'\n"
> EOF
$ hg init
$ echo a > a; hg add a; hg ci -m a
$ echo b > b; hg add b; hg ci -m b1
$ hg up 0 -q
$ echo b > b; hg add b; hg ci -m b2 -q
$ hg tglog
@ 2 'b2'
|
| o 1 'b1'
|/
o 0 'a'
With rewrite.empty-successor=skip, b2 is skipped because it would become empty.
$ hg rebase -s 2 -d 1 --config rewrite.empty-successor=skip --dry-run
starting dry-run rebase; repository will not be changed
rebasing 2:6e2aad5e0f3c tip "b2"
note: not rebasing 2:6e2aad5e0f3c tip "b2", its destination already has all its changes
dry-run rebase completed successfully; run without -n/--dry-run to perform this rebase
With rewrite.empty-successor=keep, b2 will be recreated although it became empty.
$ hg rebase -s 2 -d 1 --config rewrite.empty-successor=keep
rebasing 2:6e2aad5e0f3c tip "b2"
note: created empty successor for 2:6e2aad5e0f3c tip "b2", its destination already has all its changes
saved backup bundle to $TESTTMP/.hg/strip-backup/6e2aad5e0f3c-7d7c8801-rebase.hg
$ hg tglog
@ 2 'b2'
|
o 1 'b1'
|
o 0 'a'