view tests/test-repo-compengines.t @ 40417:49c7b701fdc2 stable

phase: add an archived phase

This phase allows for hidden changesets in the "user space". It differs from
the "internal" phase which is intended for internal by-product only. There
have been discussions at the 4.8 sprint to use such phase to speedup cleanup
after history rewriting operation.

Shipping it in the same release as the 'internal-phase' groups the associated
`requires` entry. The important bit is to have support for this phase in the
earliest version of mercurial possible. Adding the UI to manipulate this new
phase later seems fine.

The current plan for archived usage and user interface are as follow. On a
repository with internal-phase on and evolution off:

* history rewriting command set rewritten changeset in the archived phase.
  (This mean updating the cleanupnodes method).
* keep `hg unbundle .hg/strip-backup/X.hg` as a way to restore changeset for
  now
  (backup bundle need to contains phase data)
* [maybe] add a `hg strip --soft` advance flag
  (a light way to expose the feature without getting in the way of a better
  UI)

Mercurial 4.8 freeze is too close to get the above in by then.

We don't introduce a new repository `requirement` as we reuse the one
introduced with the 'archived' phase during the 4.8 cycle.

A new repository uses zlib storage, which doesn't need a requirement

  $ hg init default
  $ cd default
  $ cat .hg/requires
  dotencode
  fncache
  generaldelta
  revlogv1
  store
  testonly-simplestore (reposimplestore !)

  $ touch foo
  $ hg -q commit -A -m 'initial commit with a lot of repeated repeated repeated text to trigger compression'
  $ hg debugrevlog -c | grep 0x78
      0x78 (x)  :   1 (100.00%)
      0x78 (x)  : 110 (100.00%)

  $ cd ..

Unknown compression engine to format.compression aborts

  $ hg --config experimental.format.compression=unknown init unknown
  abort: compression engine unknown defined by experimental.format.compression not available
  (run "hg debuginstall" to list available compression engines)
  [255]

A requirement specifying an unknown compression engine results in bail

  $ hg init unknownrequirement
  $ cd unknownrequirement
  $ echo exp-compression-unknown >> .hg/requires
  $ hg log
  abort: repository requires features unknown to this Mercurial: exp-compression-unknown!
  (see https://mercurial-scm.org/wiki/MissingRequirement for more information)
  [255]

  $ cd ..

#if zstd

  $ hg --config experimental.format.compression=zstd init zstd
  $ cd zstd
  $ cat .hg/requires
  dotencode
  exp-compression-zstd
  fncache
  generaldelta
  revlogv1
  store
  testonly-simplestore (reposimplestore !)

  $ touch foo
  $ hg -q commit -A -m 'initial commit with a lot of repeated repeated repeated text'

  $ hg debugrevlog -c | grep 0x28
      0x28      :  1 (100.00%)
      0x28      : 98 (100.00%)

  $ cd ..

Specifying a new format.compression on an existing repo won't introduce data
with that engine or a requirement

  $ cd default
  $ touch bar
  $ hg --config experimental.format.compression=zstd -q commit -A -m 'add bar with a lot of repeated repeated repeated text'

  $ cat .hg/requires
  dotencode
  fncache
  generaldelta
  revlogv1
  store
  testonly-simplestore (reposimplestore !)

  $ hg debugrevlog -c | grep 0x78
      0x78 (x)  :   2 (100.00%)
      0x78 (x)  : 199 (100.00%)

#endif