view tests/test-issue1502.t @ 30745:c1b7b2285522

revlog: flag processor

Add the ability for revlog objects to process revision flags and apply
registered transforms on read/write operations.

This patch introduces:
- the 'revlog._processflags()' method that looks at revision flags and applies
  flag processors registered on them. Due to the need to handle non-commutative
  operations, flag transforms are applied in stable order but the order in which
  the transforms are applied is reversed between read and write operations.
- the 'addflagprocessor()' method allowing to register processors on flags.
  Flag processors are defined as a 3-tuple of (read, write, raw) functions to be
  applied depending on the operation being performed.
- an update on 'revlog.addrevision()' behavior. The current flagprocessor design
  relies on extensions to wrap around 'addrevision()' to set flags on revision
  data, and on the flagprocessor to perform the actual transformation of its
  contents. In the lfs case, this means we need to process flags before we meet
  the 2GB size check, leading to performing some operations before it happens:
  - if flags are set on the revision data, we assume some extensions might be
    modifying the contents using the flag processor next, and we compute the
    node for the original revision data (still allowing extension to override
    the node by wrapping around 'addrevision()').
  - we then invoke the flag processor to apply registered transforms (in lfs's
    case, drastically reducing the size of large blobs).
  - finally, we proceed with the 2GB size check.

Note: In the case a cachedelta is passed to 'addrevision()' and we detect the
flag processor modified the revision data, we chose to trust the flag processor
and drop the cachedelta.

https://bz.mercurial-scm.org/1502

Initialize repository

  $ hg init foo
  $ touch foo/a && hg -R foo commit -A -m "added a"
  adding a

  $ hg clone foo foo1
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ echo "bar" > foo1/a && hg -R foo1 commit -m "edit a in foo1"
  $ echo "hi" > foo/a && hg -R foo commit -m "edited a foo"
  $ hg -R foo1 pull
  pulling from $TESTTMP/foo (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)

  $ hg -R foo1 book branchy
  $ hg -R foo1 book
   * branchy                   1:e3e522925eff

Pull. Bookmark should not jump to new head.

  $ echo "there" >> foo/a && hg -R foo commit -m "edited a again"
  $ hg -R foo1 pull
  pulling from $TESTTMP/foo (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  (run 'hg update' to get a working copy)

  $ hg -R foo1 book
   * branchy                   1:e3e522925eff