config: explicitly track the use of the standard default value
We introduce a small object used to detect that no specific default value has
been passed to 'ui.config'. We need this explicit special value since "None" is
a valid and common default value.
The end goal here is to make progress on a centralised and explicit declaration
of the available config option. A first good usecase for this are "default"
value. Before starting looking further down this alley we needs to rework the
handling of default value in the 'ui' object to have all configxyz methods going
through the same logic. This is the first changeset on this trek.
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-revlogv2.0
fncache
store
$ hg log
Unknown flags to revlog are rejected
>>> with open('.hg/store/00changelog.i', 'wb') as fh:
... fh.write('\x00\x04\xde\xad')
$ hg log
abort: unknown flags (0x04) in version 57005 revlog 00changelog.i!
[255]
$ 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 (changelog always disables generaldelta)
$ 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 03 de ad |....|