nodemap: gate the feature behind a new requirement
Now that the feature is working smoothly, a question was still open, should we
gate the feature behind a new requirement or just treat it as a cache to be
warmed by those who can and ignored by other.
The advantage of using the cache approach is a transparent upgrade/downgrade
story, making the feature easier to move to. However having out of date cache
can come with a significant performance hit for process who expect an up to
date cache but found none. In this case the file needs to be stored under
`.hg/cache`.
The "requirement" approach guarantee that the persistent nodemap is up to date.
However, it comes with a less flexible activation story since an explicite
upgrade is required. In this case the file can be stored in `.hg/store`.
This wiki page is relevant to this questions:
https://www.mercurial-scm.org/wiki/ComputedIndexPlan
So which one should we take? Another element came into plan, the persistent
nodemap use the `add` method of the transaction, it is used to keep track of a
file content before a transaction in case we need to rollback it back. It turns
out that the `transaction.add` API does not support file stored anywhere than
`.hg/store`. Making it support file stored elsewhere is possible, require a
change in on disk transaction format. Updating on disk file requires…
introducing a new requirements.
As a result, we pick the second option "gating the persistent nodemap behind a
new requirements".
Differential Revision: https://phab.mercurial-scm.org/D8417
Test hg log changeset printer external hook
-------------------------------------------
$ cat > $TESTTMP/logexthook.py <<EOF
> from __future__ import absolute_import
> import codecs
> from mercurial import (
> commands,
> logcmdutil,
> repair,
> )
> def brot13(b):
> return codecs.encode(b.decode('utf8'), 'rot-13').encode('utf8')
> def rot13description(self, ctx):
> description = ctx.description().strip().splitlines()[0]
> self.ui.write(b"%s: %s\n" % (brot13(b"summary"),
> brot13(description)))
> def reposetup(ui, repo):
> logcmdutil.changesetprinter._exthook = rot13description
> EOF
Prepare the repository
$ hg init empty
$ cd empty
$ touch ROOT
$ hg commit -A -m "Root" ROOT
$ touch a b c
$ hg commit -A -m "Add A, B, C" a b c
Check the log
$ hg log --config extensions.t=$TESTTMP/logexthook.py
changeset: 1:70fc82b23320
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
fhzznel: Nqq N, O, P
summary: Add A, B, C
changeset: 0:b00443a54871
user: test
date: Thu Jan 01 00:00:00 1970 +0000
fhzznel: Ebbg
summary: Root
Check that exthook is working with graph log too
$ hg log -G --config extensions.t=$TESTTMP/logexthook.py
@ changeset: 1:70fc82b23320
| tag: tip
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| fhzznel: Nqq N, O, P
| summary: Add A, B, C
|
o changeset: 0:b00443a54871
user: test
date: Thu Jan 01 00:00:00 1970 +0000
fhzznel: Ebbg
summary: Root