revlog: skeleton support for version 2 revlogs
There are a number of improvements we want to make to revlogs
that will require a new version - version 2. It is unclear what the
full set of improvements will be or when we'll be done with them.
What I do know is that the process will likely take longer than a
single release, will require input from various stakeholders to
evaluate changes, and will have many contentious debates and
bikeshedding.
It is unrealistic to develop revlog version 2 up front: there
are just too many uncertainties that we won't know until things
are implemented and experiments are run. Some changes will also
be invasive and prone to bit rot, so sitting on dozens of patches
is not practical.
This commit introduces skeleton support for version 2 revlogs in
a way that is flexible and not bound by backwards compatibility
concerns.
An experimental repo requirement for denoting revlog v2 has been
added. The requirement string has a sub-version component to it.
This will allow us to declare multiple requirements in the course
of developing revlog v2. Whenever we change the in-development
revlog v2 format, we can tweak the string, creating a new
requirement and locking out old clients. This will allow us to
make as many backwards incompatible changes and experiments to
revlog v2 as we want. In other words, we can land code and make
meaningful progress towards revlog v2 while still maintaining
extreme format flexibility up until the point we freeze the
format and remove the experimental labels.
To enable the new repo requirement, you must supply an experimental
and undocumented config option. But not just any boolean flag
will do: you need to explicitly use a value that no sane person
should ever type. This is an additional guard against enabling
revlog v2 on an installation it shouldn't be enabled on. The
specific scenario I'm trying to prevent is say a user with a
4.4 client with a frozen format enabling the option but then
downgrading to 4.3 and accidentally creating repos with an
outdated and unsupported repo format. Requiring a "challenge"
string should prevent this.
Because the format is not yet finalized and I don't want to take
any chances, revlog v2's version is currently 0xDEAD. I figure
squatting on a value we're likely never to use as an actual revlog
version to mean "internal testing only" is acceptable. And
"dead" is easily recognized as something meaningful.
There is a bunch of cleanup that is needed before work on revlog
v2 begins in earnest. I plan on doing that work once this patch
is accepted and we're comfortable with the idea of starting down
this path.
$ hg init repo
$ cd repo
$ hg init subrepo
$ echo a > subrepo/a
$ hg -R subrepo ci -Am adda
adding a
$ echo 'subrepo = subrepo' > .hgsub
$ hg ci -Am addsubrepo
adding .hgsub
$ echo b > subrepo/b
$ hg -R subrepo ci -Am addb
adding b
$ hg ci -m updatedsub
ignore blanklines in .hgsubstate
>>> file('.hgsubstate', 'wb').write('\n\n \t \n \n')
$ hg st --subrepos
M .hgsubstate
$ hg revert -qC .hgsubstate
abort more gracefully on .hgsubstate parsing error
$ cp .hgsubstate .hgsubstate.old
>>> file('.hgsubstate', 'wb').write('\ninvalid')
$ hg st --subrepos --cwd $TESTTMP -R $TESTTMP/repo
abort: invalid subrepository revision specifier in 'repo/.hgsubstate' line 2
[255]
$ mv .hgsubstate.old .hgsubstate
delete .hgsub and revert it
$ rm .hgsub
$ hg revert .hgsub
warning: subrepo spec file '.hgsub' not found
warning: subrepo spec file '.hgsub' not found
delete .hgsubstate and revert it
$ rm .hgsubstate
$ hg revert .hgsubstate
delete .hgsub and update
$ rm .hgsub
$ hg up 0 --cwd $TESTTMP -R $TESTTMP/repo
warning: subrepo spec file 'repo/.hgsub' not found
warning: subrepo spec file 'repo/.hgsub' not found
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg st
warning: subrepo spec file '.hgsub' not found
! .hgsub
$ ls subrepo
a
delete .hgsubstate and update
$ hg up -C
warning: subrepo spec file '.hgsub' not found
warning: subrepo spec file '.hgsub' not found
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm .hgsubstate
$ hg up 0
other [destination] changed .hgsubstate which local [working copy] deleted
use (c)hanged version or leave (d)eleted? c
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg st
$ ls subrepo
a
Enable obsolete
$ cat >> $HGRCPATH << EOF
> [ui]
> logtemplate= {rev}:{node|short} {desc|firstline}
> [phases]
> publish=False
> [experimental]
> evolution=createmarkers
> EOF
check that we can update parent repo with missing (amended) subrepo revision
$ hg up --repository subrepo -r tip
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg ci -m "updated subrepo to tip"
created new head
$ cd subrepo
$ hg update -r tip
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo foo > a
$ hg commit --amend -m "addb (amended)"
$ cd ..
$ hg update --clean .
revision 102a90ea7b4a in subrepo subrepo is hidden
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
check that --hidden is propagated to the subrepo
$ hg -R subrepo up tip
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg ci -m 'commit with amended subrepo'
$ echo bar > subrepo/a
$ hg -R subrepo ci --amend -m "amend a (again)"
$ hg --hidden cat subrepo/a
foo
verify will warn if locked-in subrepo revisions are hidden or missing
$ hg ci -m "amended subrepo (again)"
$ hg --config extensions.strip= --hidden strip -R subrepo -qr 'tip' --config devel.strip-obsmarkers=no
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
2 files, 5 changesets, 5 total revisions
checking subrepo links
subrepo 'subrepo' is hidden in revision a66de08943b6
subrepo 'subrepo' is hidden in revision 674d05939c1e
subrepo 'subrepo' not found in revision a7d05d9055a4
verifying shouldn't init a new subrepo if the reference doesn't exist
$ mv subrepo b
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
2 files, 5 changesets, 5 total revisions
checking subrepo links
0: repository $TESTTMP/repo/subrepo not found (glob)
1: repository $TESTTMP/repo/subrepo not found (glob)
3: repository $TESTTMP/repo/subrepo not found (glob)
4: repository $TESTTMP/repo/subrepo not found (glob)
$ ls
b
$ mv b subrepo
$ cd ..