dirstate-v2: no longer register the data-file during transaction
If the data file change during the transaction, we cannot truncate it.
The content of the file itself is fine as it will get backed up at the same time
as the docket.
Leaving the trailing data at the end of failed transaction is fine. The
dirstate-v2 format supports it. The dead data will simply we written over if
necessary.
Testing that convert.hg.preserve-hash=true can be used to make hg
convert from hg repo to hg repo preserve hashes, even if the
computation of the files list in commits change slightly between hg
versions.
$ cat <<'EOF' >> "$HGRCPATH"
> [extensions]
> convert =
> EOF
$ cat <<'EOF' > changefileslist.py
> from mercurial import (changelog, extensions, metadata)
> def wrap(orig, clog, manifest, files, *args, **kwargs):
> files = metadata.ChangingFiles(touched=[b"a"])
> return orig(clog, manifest, files, *args, **kwargs)
> def extsetup(ui):
> extensions.wrapfunction(changelog.changelog, 'add', wrap)
> EOF
$ hg init repo
$ cd repo
$ echo a > a; hg commit -qAm a
$ echo b > a; hg commit -qAm b
$ hg up -qr 0; echo c > c; hg commit -qAm c
$ hg merge -qr 1
$ hg commit -m_ --config extensions.x=../changefileslist.py
$ hg log -r . -T '{node|short} {files|json}\n'
c085bbe93d59 ["a"]
Now that we have a commit with a files list that's not what the
current hg version would create, check that convert either fixes it or
keeps it depending on config:
$ hg convert -q . ../convert
$ hg --cwd ../convert log -r tip -T '{node|short} {files|json}\n'
b7c4d4bbacd3 []
$ rm -rf ../convert
$ hg convert -q . ../convert --config convert.hg.preserve-hash=true
$ hg --cwd ../convert log -r tip -T '{node|short} {files|json}\n'
c085bbe93d59 ["a"]
$ rm -rf ../convert