view tests/test-convert-clonebranches.t @ 33289:abd7dedbaa36

sparse: vendor Facebook-developed extension

Facebook has developed an extension to enable "sparse" checkouts -
a working directory with a subset of files. This feature is a critical
component in enabling repositories to scale to infinite number of
files while retaining reasonable performance. It's worth noting
that sparse checkout is only one possible solution to this problem:
another is virtual filesystems that realize files on first access.
But given that virtual filesystems may not be accessible to all
users, sparse checkout is necessary as a fallback.

Per mailing list discussion at
https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-March/095868.html
we want to add sparse checkout to the Mercurial distribution via
roughly the following mechanism:

1. Vendor extension as-is with minimal modifications (this patch)
2. Refactor extension so it is more clearly experimental and inline
   with Mercurial practices
3. Move code from extension into core where possible
4. Drop experimental labeling and/or move feature into core
   after sign-off from narrow clone feature owners

This commit essentially copies the sparse extension and tests
from revision 71e0a2aeca92a4078fe1b8c76e32c88ff1929737 of the
https://bitbucket.org/facebook/hg-experimental repository.

A list of modifications made as part of vendoring is as follows:

* "EXPERIMENTAL" added to module docstring
* Imports were changed to match Mercurial style conventions
* "testedwith" value was updated to core Mercurial special value and
  comment boilerplate was inserted
* A "clone_sparse" function was renamed to "clonesparse" to appease
  the style checker
* Paths to the sparse extension in tests reflect built-in location
* test-sparse-extensions.t was renamed to test-sparse-fsmonitor.t
  and references to "simplecache" were removed. The test always skips
  because it isn't trivial to run it given the way we currently run
  fsmonitor tests
* A double empty line was removed from test-sparse-profiles.t

There are aspects of the added code that are obviously not ideal.
The goal is to make a minimal number of modifications as part of
the vendoring to make it easier to track changes from the original
implementation. Refactoring will occur in subsequent patches.

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > convert =
  > [convert]
  > hg.tagsbranch = 0
  > EOF
  $ hg init source
  $ cd source
  $ echo a > a
  $ hg ci -qAm adda

Add a merge with one parent in the same branch

  $ echo a >> a
  $ hg ci -qAm changea
  $ hg up -qC 0
  $ hg branch branch0
  marked working directory as branch branch0
  (branches are permanent and global, did you want a bookmark?)
  $ echo b > b
  $ hg ci -qAm addb
  $ hg up -qC
  $ hg merge default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -qm mergeab
  $ hg tag -ql mergeab
  $ cd ..

Miss perl... sometimes

  $ cat > filter.py <<EOF
  > import sys, re
  > 
  > r = re.compile(r'^(?:\d+|pulling from)')
  > sys.stdout.writelines([l for l in sys.stdin if r.search(l)])
  > EOF

convert

  $ hg convert -v --config convert.hg.clonebranches=1 source dest |
  >     $PYTHON filter.py
  3 adda
  2 changea
  1 addb
  pulling from default into branch0
  1 changesets found
  0 mergeab
  pulling from default into branch0
  1 changesets found

Add a merge with both parents and child in different branches

  $ cd source
  $ hg branch branch1
  marked working directory as branch branch1
  $ echo a > file1
  $ hg ci -qAm c1
  $ hg up -qC mergeab
  $ hg branch branch2
  marked working directory as branch branch2
  $ echo a > file2
  $ hg ci -qAm c2
  $ hg merge branch1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg branch branch3
  marked working directory as branch branch3
  $ hg ci -qAm c3
  $ cd ..

incremental conversion

  $ hg convert -v --config convert.hg.clonebranches=1 source dest |
  >     $PYTHON filter.py
  2 c1
  pulling from branch0 into branch1
  4 changesets found
  1 c2
  pulling from branch0 into branch2
  4 changesets found
  0 c3
  pulling from branch1 into branch3
  5 changesets found
  pulling from branch2 into branch3
  1 changesets found