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 However having out of date cache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 sparse
$ hg init myrepo
$ cd myrepo
$ cat >> $HGRCPATH <<EOF
> [extensions]
> sparse=
> purge=
> strip=
> rebase=
> EOF
$ echo a > index.html
$ echo x > data.py
$ echo z > readme.txt
$ cat > base.sparse <<EOF
> [include]
> *.sparse
> EOF
$ hg ci -Aqm 'initial'
$ cat > webpage.sparse <<EOF
> %include base.sparse
> [include]
> *.html
> EOF
$ hg ci -Aqm 'initial'
Import a rules file against a 'blank' sparse profile
$ cat > $TESTTMP/rules_to_import <<EOF
> [include]
> *.py
> EOF
$ hg debugsparse --import-rules $TESTTMP/rules_to_import
$ ls -A
.hg
data.py
$ hg debugsparse --reset
$ rm .hg/sparse
$ cat > $TESTTMP/rules_to_import <<EOF
> %include base.sparse
> [include]
> *.py
> EOF
$ hg debugsparse --import-rules $TESTTMP/rules_to_import
$ ls -A
.hg
base.sparse
data.py
webpage.sparse
$ hg debugsparse --reset
$ rm .hg/sparse
Start against an existing profile; rules *already active* should be ignored
$ hg debugsparse --enable-profile webpage.sparse
$ hg debugsparse --include *.py
$ cat > $TESTTMP/rules_to_import <<EOF
> %include base.sparse
> [include]
> *.html
> *.txt
> [exclude]
> *.py
> EOF
$ hg debugsparse --import-rules $TESTTMP/rules_to_import
$ ls -A
.hg
base.sparse
index.html
readme.txt
webpage.sparse
$ cat .hg/sparse
%include webpage.sparse
[include]
*.py
*.txt
[exclude]
*.py
$ hg debugsparse --reset
$ rm .hg/sparse
Same tests, with -Tjson enabled to output summaries
$ cat > $TESTTMP/rules_to_import <<EOF
> [include]
> *.py
> EOF
$ hg debugsparse --import-rules $TESTTMP/rules_to_import -Tjson
[
{
"exclude_rules_added": 0,
"files_added": 0,
"files_conflicting": 0,
"files_dropped": 4,
"include_rules_added": 1,
"profiles_added": 0
}
]
$ hg debugsparse --reset
$ rm .hg/sparse
$ cat > $TESTTMP/rules_to_import <<EOF
> %include base.sparse
> [include]
> *.py
> EOF
$ hg debugsparse --import-rules $TESTTMP/rules_to_import -Tjson
[
{
"exclude_rules_added": 0,
"files_added": 0,
"files_conflicting": 0,
"files_dropped": 2,
"include_rules_added": 1,
"profiles_added": 1
}
]
$ hg debugsparse --reset
$ rm .hg/sparse
$ hg debugsparse --enable-profile webpage.sparse
$ hg debugsparse --include *.py
$ cat > $TESTTMP/rules_to_import <<EOF
> %include base.sparse
> [include]
> *.html
> *.txt
> [exclude]
> *.py
> EOF
$ hg debugsparse --import-rules $TESTTMP/rules_to_import -Tjson
[
{
"exclude_rules_added": 1,
"files_added": 1,
"files_conflicting": 0,
"files_dropped": 1,
"include_rules_added": 1,
"profiles_added": 0
}
]
If importing results in no new rules being added, no refresh should take place!
$ cat > $TESTTMP/trap_sparse_refresh.py <<EOF
> from mercurial import error, sparse
> def extsetup(ui):
> def abort_refresh(*args, **kwargs):
> raise error.Abort('sparse._refresh called!')
> sparse.refreshwdir = abort_refresh
> EOF
$ cat >> $HGRCPATH <<EOF
> [extensions]
> trap_sparse_refresh=$TESTTMP/trap_sparse_refresh.py
> EOF
$ cat > $TESTTMP/rules_to_import <<EOF
> [include]
> *.py
> EOF
$ hg debugsparse --import-rules $TESTTMP/rules_to_import
If an exception is raised during refresh, restore the existing rules again.
$ cat > $TESTTMP/rules_to_import <<EOF
> [exclude]
> *.html
> EOF
$ hg debugsparse --import-rules $TESTTMP/rules_to_import
abort: sparse._refresh called!
[255]
$ cat .hg/sparse
%include webpage.sparse
[include]
*.py
*.txt
[exclude]
*.py