test: extract some generic data and utility from test-rust-ancestor.py
We will reuse this for more tests related to revlog index. In pratice this
series of changesets add an index implementation provided from Rust and we want
to be able to test it.
Differential Revision: https://phab.mercurial-scm.org/D7652
#require unix-permissions no-root
$ hg init a
$ cd a
$ echo foo > b
$ hg add b
$ hg ci -m "b"
$ chmod -w .hg/store
$ cd ..
$ hg clone a b
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets 97310831fa1a
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ chmod +w a/.hg/store # let test clean up
$ cd b
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
checked 1 changesets with 1 changes to 1 files
$ cd ..