view tests/test-revlog-packentry.t @ 20275:2123d27ff75d

backout: avoid update on simple case.

Before the changeset the backout process was:
1) go to <target>
2) revert to <target> parent
3) update back to changeset we came from

The two update steps can takes a very long time to move back and forth unrelated
file change between <target> and current working directory.

The new process is just merging current working directory with the parent of
<target> using <target> as ancestor. This give the very same result but skip
the two updates. On big repo with a lot of files and changes that save a lots of
time (x20 for one week window).

The "merge" version (hg backout --merge) is still done with upgrades. We could
imagine using in memory commit to speed it up but this is another fish.

  $ hg init repo
  $ cd repo

  $ touch foo
  $ hg ci -Am 'add foo'
  adding foo

  $ hg up -C null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

this should be stored as a delta against rev 0

  $ echo foo bar baz > foo
  $ hg ci -Am 'add foo again'
  adding foo
  created new head

  $ hg debugindex foo
     rev    offset  length  ..... linkrev nodeid       p1           p2 (re)
       0         0       0  .....       0 b80de5d13875 000000000000 000000000000 (re)
       1         0      24  .....       1 0376abec49b8 000000000000 000000000000 (re)

  $ cd ..