revlog: move censor logic out of censor extension
The censor extension is doing very low-level things with revlogs.
It is fundamentally impossible for this logic to remain in the censor
extension while support multiple storage backends: we need each
storage backend to implement censor in its own storage-specific
way.
This commit effectively moves the revlog-specific censoring code to
be a method of revlogs themselves.
We've defined a new API on the file storage interface for censoring
an individual node. Even though the current censoring code doesn't
use it, the API requires a transaction instance because it logically
makes sense for storage backends to require an active transaction
(which implies a held write lock) in order to rewrite storage.
After this commit, the censor extension has been reduced to
boilerplate precondition checking before invoking the generic
storage API.
I tried to keep the code as similar as possible. But some minor
changes were made:
* We use self._io instead of instantiating a new revlogio instance.
* We compare self.version against REVLOGV0 instead of != REVLOGV1
because presumably all future revlog versions will support censoring.
* We use self.opener instead of going through repo.svfs (we don't have
a handle on the repo instance from a revlog).
* "revlog" dropped
* Replace "flog" with "self".
Differential Revision: https://phab.mercurial-scm.org/D4656
Do not strip innocent children. See https://bitbucket.org/facebook/hg-experimental/issues/6/hg-absorb-merges-diverged-commits
$ cat >> $HGRCPATH << EOF
> [extensions]
> absorb=
> drawdag=$TESTDIR/drawdag.py
> EOF
$ hg init
$ hg debugdrawdag << EOF
> E
> |
> D F
> |/
> C
> |
> B
> |
> A
> EOF
$ hg up E -q
$ echo 1 >> B
$ echo 2 >> D
$ hg absorb
saved backup bundle to * (glob)
2 of 2 chunk(s) applied
$ hg log -G -T '{desc}'
@ E
|
o D
|
o C
|
o B
|
| o F
| |
| o C
| |
| o B
|/
o A