hg-core: make `Index` owner of its bytes (D8958#inline-14994 followup 1/2)
Prevent building `Index` every time it is needed. It was a bad idea anyway.
When `Index::new` will return `Result` it will avoid things like `Revlog::len`
returning `Result<usize>` instead of `usize`.
[X] make `Index` owner of its bytes
[ ] make `Index::new` return an error if `offset != bytes.len()`
Differential Revision: https://phab.mercurial-scm.org/D9106
https://bz.mercurial-scm.org/612
$ hg init
$ mkdir src
$ echo a > src/a.c
$ hg ci -Ama
adding src/a.c
$ hg mv src source
moving src/a.c to source/a.c
$ hg ci -Ammove
$ hg co -C 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo new > src/a.c
$ echo compiled > src/a.o
$ hg ci -mupdate
created new head
$ hg status
? src/a.o
$ hg merge
merging src/a.c and source/a.c to source/a.c
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg status
M source/a.c
R src/a.c
? src/a.o