requirements: no longer drop `generaldelta` requirement with revlogv2
A repository could use a mix of revlogv1 and revlogv2, making the requirements
still necessary. Overall we should move away from the "requirements" file being
used a way to configure the repository and stick to it "what do you need to
access this repository". However this is a wider work for another time.
In addition the logic we just dropped was confusing the `hg debugformat`
command, breaking the upgrade code and inconsistent (eg: `sparse-revlog` is also
implied by `revlogv2`).
Finally, multiple other config option would imply the use of the `revlogv2`
requirements, without drop the `generaldelta` one, leading to more
inconsistency.
Differential Revision: https://phab.mercurial-scm.org/D10612
#require reporevlogstore
A repo with unknown revlogv2 requirement string cannot be opened
$ hg init invalidreq
$ cd invalidreq
$ echo exp-revlogv2.unknown >> .hg/requires
$ hg log
abort: repository requires features unknown to this Mercurial: exp-revlogv2.unknown
(see https://mercurial-scm.org/wiki/MissingRequirement for more information)
[255]
$ cd ..
Can create and open repo with revlog v2 requirement
$ cat >> $HGRCPATH << EOF
> [experimental]
> revlogv2 = enable-unstable-format-and-corrupt-my-data
> EOF
$ hg init empty-repo
$ cd empty-repo
$ cat .hg/requires
dotencode
exp-revlogv2.2
fncache
generaldelta
persistent-nodemap (rust !)
revlog-compression-zstd (zstd !)
sparserevlog
store
$ hg log
Unknown flags to revlog are rejected
>>> with open('.hg/store/00changelog.i', 'wb') as fh:
... fh.write(b'\xff\x00\xde\xad') and None
$ hg log
abort: unknown flags (0xff00) in version 57005 revlog 00changelog
[50]
$ cd ..
Writing a simple revlog v2 works
$ hg init simple
$ cd simple
$ touch foo
$ hg -q commit -A -m initial
$ hg log
changeset: 0:96ee1d7354c4
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: initial
Header written as expected
$ f --hexdump --bytes 4 .hg/store/00changelog.i
.hg/store/00changelog.i:
0000: 00 01 de ad |....|
$ f --hexdump --bytes 4 .hg/store/data/foo.i
.hg/store/data/foo.i:
0000: 00 01 de ad |....|