view tests/test-single-head.t @ 40393:229d23cdb203

exchangev2: support fetching shallow files history

This commit teaches the exchangev2 client code to handle fetching shallow
files data.

Only shallow fetching of files data is supported: shallow fetching of
changeset and manifest data is explicitly not yet supported.

Previously, we would fetch file revisions for changesets that were received
by the current pull operation. In the new model, we calculate the set of
"relevant" changesets given the pull depth and only fetch files data for
those changesets.

We also teach the "filesdata" command invocation to vary parameters as needed.

The implementation here is far from complete or optimal. Subsequent pulls will
end up re-fetching a lot of files data. But the application of this data should
mostly be a no-op on the client, so it isn't a big deal.

Depending on the order file revisions are fetched in, revisions could get
inserted with the wrong revision number relationships. I think the best way
to deal with this is to remove revision numbers from storage and to either
dynamically derive them (by reconstructing a DAG from nodes/parents) or remove
revision numbers from the file storage interface completely.

A missing API that we'll likely want to write pretty soon is "ensure files
for revision(s) are present." We can kind of cajole exchangev2.pull() to do
this. But it isn't very efficient. For example, in simple cases like
widening the store to obtain data for a single revision, it is probably
more efficient to walk the manifest and find exactly which file revisions
are missing and to make explicit requests for just their data. In more
advanced cases, asking the server for all files data may be more efficient,
even though it requires sending data the client already has. There is tons
of room for future experimentation here. And TBH I'm not sure what the
final state will be.

Anyway, this commit gets us pretty close to being able to have shallow
and narrow checkouts with exchangev2/sqlite storage. Close enough that a
minimal extension should be able to provide fill in the gaps until the code
in core stabilizes and there is a user-facing way to trigger the
narrow/shallow bits from `hg clone` without also implying using of the
narrow extension...

Differential Revision: https://phab.mercurial-scm.org/D5169

=====================
Test workflow options
=====================

  $ . "$TESTDIR/testlib/obsmarker-common.sh"

Test single head enforcing - Setup
=============================================

  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > evolution = all
  > EOF
  $ hg init single-head-server
  $ cd single-head-server
  $ cat <<EOF >> .hg/hgrc
  > [phases]
  > publish = no
  > [experimental]
  > single-head-per-branch = yes
  > EOF
  $ mkcommit ROOT
  $ mkcommit c_dA0
  $ cd ..

  $ hg clone single-head-server client
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

Test single head enforcing - with branch only
---------------------------------------------

  $ cd client

continuing the current defaultbranch

  $ mkcommit c_dB0
  $ hg push
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files

creating a new branch

  $ hg up 'desc("ROOT")'
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg branch branch_A
  marked working directory as branch branch_A
  (branches are permanent and global, did you want a bookmark?)
  $ mkcommit c_aC0
  $ hg push --new-branch
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)

Create a new head on the default branch

  $ hg up 'desc("c_dA0")'
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit c_dD0
  created new head
  $ hg push -f
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  transaction abort!
  rollback completed
  abort: rejecting multiple heads on branch "default"
  (2 heads: 286d02a6e2a2 9bf953aa81f6)
  [255]

remerge them

  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ mkcommit c_dE0
  $ hg push
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files

Test single head enforcing - after rewrite
------------------------------------------

  $ mkcommit c_dF0
  $ hg push
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  $ hg commit --amend -m c_dF1
  $ hg push
  pushing to $TESTTMP/single-head-server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 1 files (+1 heads)
  1 new obsolescence markers
  obsoleted 1 changesets

Check it does to interfer with strip
------------------------------------

setup

  $ hg branch branch_A --force
  marked working directory as branch branch_A
  $ mkcommit c_aG0
  created new head
  $ hg update 'desc("c_dF1")'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit c_dH0
  $ hg update 'desc("c_aG0")'
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ mkcommit c_aI0
  $ hg log -G
  @    changeset:   10:49003e504178
  |\   branch:      branch_A
  | |  tag:         tip
  | |  parent:      8:a33fb808fb4b
  | |  parent:      3:840af1c6bc88
  | |  user:        test
  | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | |  summary:     c_aI0
  | |
  | | o  changeset:   9:fe47ea669cea
  | | |  parent:      7:99a2dc242c5d
  | | |  user:        test
  | | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | | |  summary:     c_dH0
  | | |
  | o |  changeset:   8:a33fb808fb4b
  | |/   branch:      branch_A
  | |    user:        test
  | |    date:        Thu Jan 01 00:00:00 1970 +0000
  | |    summary:     c_aG0
  | |
  | o  changeset:   7:99a2dc242c5d
  | |  parent:      5:6ed1df20edb1
  | |  user:        test
  | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | |  summary:     c_dF1
  | |
  | o    changeset:   5:6ed1df20edb1
  | |\   parent:      4:9bf953aa81f6
  | | |  parent:      2:286d02a6e2a2
  | | |  user:        test
  | | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | | |  summary:     c_dE0
  | | |
  | | o  changeset:   4:9bf953aa81f6
  | | |  parent:      1:134bc3852ad2
  | | |  user:        test
  | | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | | |  summary:     c_dD0
  | | |
  o | |  changeset:   3:840af1c6bc88
  | | |  branch:      branch_A
  | | |  parent:      0:ea207398892e
  | | |  user:        test
  | | |  date:        Thu Jan 01 00:00:00 1970 +0000
  | | |  summary:     c_aC0
  | | |
  | o |  changeset:   2:286d02a6e2a2
  | |/   user:        test
  | |    date:        Thu Jan 01 00:00:00 1970 +0000
  | |    summary:     c_dB0
  | |
  | o  changeset:   1:134bc3852ad2
  |/   user:        test
  |    date:        Thu Jan 01 00:00:00 1970 +0000
  |    summary:     c_dA0
  |
  o  changeset:   0:ea207398892e
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     ROOT
  

actual stripping

  $ hg strip --config extensions.strip= --rev 'desc("c_dH0")'
  saved backup bundle to $TESTTMP/client/.hg/strip-backup/fe47ea669cea-a41bf5a9-backup.hg