branchcache: add a "pure topological head" fast path In a narrow but actually quick common case, all topological heads are all on the same branch and all open. In this case, computing the branch map is very simple. We can quickly detect situation where this situation will not change. So we update the V3 format to be able to express this situation and upgrade the update code to detect we remains in that mode. The branch cache is populated with the actual value when the branch map is accessed, but the update_disk method can do the update without needing to populate it.

     1

  $ hg init repo

     2

  $ cd repo

     3

     4

  $ touch foo

     5

  $ hg ci -Am 'add foo'

     6

  adding foo

     7

     8

  $ hg up -C null

     9

  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

    10

    11

this should be stored as a delta against rev 0

    12

    13

  $ echo foo bar baz > foo

    14

  $ hg ci -Am 'add foo again'

    15

  adding foo

    16

  created new head

    17

    18

  $ hg debugindex foo

    19

     rev linkrev       nodeid    p1-nodeid    p2-nodeid

    20

       0       0 b80de5d13875 000000000000 000000000000

    21

       1       1 0376abec49b8 000000000000 000000000000

    22

    23

  $ cd ..