sqlitestore: support for storing revisions without their parents
This commit kinda/sorta implements the equivalent of ellipsis nodes for
the SQLite storage backend.
Without implementing full blown ellipsis nodes (and the necessary support for
them in the wire protocol), we instead teach the store to rewrite the p1 and
p2 nodes to nullid when the incoming parent isn't in the local store. This allows
servers to remain dumb and send the real parent and have the clients deal
with the missing parent problem.
This obviously isn't ideal because a benefit of ellipsis nodes is we can
insert a fake parent to ellide missing changesets. But neither solution is
ideal because it drops the original parent from storage. We could probably
teach the SQLite store to retain the original parent and handle missing
parents at read time. However, parent revisions are stored as integers and
it isn't trivial to store an "empty" revision in the store yet, which would
be necessary to represent the "missing" parent.
The store is somewhat intelligent in trying to remove the missing parents
metadata when the revision is re-added. But, revision numbers will be all
messed up in that case, so I'm not sure it is worth it. At some point we'll
likely want to remove the concept of revision numbers from the database and
have the store invent them at index generation time. Or even better, we can
do away with revision numbers from the file storage interface completely.
We'll get there eventually...
Differential Revision: https://phab.mercurial-scm.org/D5168
#require no-msys # MSYS will translate web paths as if they were file paths
This is a test of the wire protocol over CGI-based hgweb.
initialize repository
$ hg init test
$ cd test
$ echo a > a
$ hg ci -Ama
adding a
$ cd ..
$ cat >hgweb.cgi <<HGWEB
> #
> # An example CGI script to use hgweb, edit as necessary
> import cgitb
> cgitb.enable()
> from mercurial import demandimport; demandimport.enable()
> from mercurial.hgweb import hgweb
> from mercurial.hgweb import wsgicgi
> application = hgweb(b"test", b"Empty test repository")
> wsgicgi.launch(application)
> HGWEB
$ chmod 755 hgweb.cgi
try hgweb request
$ . "$TESTDIR/cgienv"
$ QUERY_STRING="cmd=changegroup&roots=0000000000000000000000000000000000000000"; export QUERY_STRING
$ "$PYTHON" hgweb.cgi >page1 2>&1
$ "$PYTHON" "$TESTDIR/md5sum.py" page1
1f424bb22ec05c3c6bc866b6e67efe43 page1
make sure headers are sent even when there is no body
$ QUERY_STRING="cmd=listkeys&namespace=nosuchnamespace" "$PYTHON" hgweb.cgi
Status: 200 Script output follows\r (esc)
Content-Type: application/mercurial-0.1\r (esc)
Content-Length: 0\r (esc)
\r (esc)