rust-revlog: make `IndexEntryBuilder` build a whole entry
The `IndexEntryBuilder` we have in tests only built part of a revlog
entry before this patch. It's more useful if it can build a full
entry. As part of fixing that, I also added a (non-test)
`IndexEntry::link_revision()`.
Differential Revision: https://phab.mercurial-scm.org/D12564
#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 ..