metadataonlyctx: don't crash when reusing the manifest with deletions
This was originally fixed by Mateusz Kwapich for the `metaedit` command in
fb-hgext with a test for the `metaedit` command. It didn't get upstreamed
because `metaedit` was not in core.
This patch fixes the crash and adds a test about `metadataonlyctx` to
avoid future regressions.
Differential Revision: https://phab.mercurial-scm.org/D550
$ hg init a
$ cd a
$ echo 123 > a
$ hg add a
$ hg commit -m "a" -u a
$ cd ..
$ hg init b
$ cd b
$ echo 321 > b
$ hg add b
$ hg commit -m "b" -u b
$ hg pull ../a
pulling from ../a
searching for changes
abort: repository is unrelated
[255]
$ hg pull -f ../a
pulling from ../a
searching for changes
warning: repository is unrelated
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg heads
changeset: 1:9a79c33a9db3
tag: tip
parent: -1:000000000000
user: a
date: Thu Jan 01 00:00:00 1970 +0000
summary: a
changeset: 0:01f8062b2de5
user: b
date: Thu Jan 01 00:00:00 1970 +0000
summary: b
$ cd ..