view tests/test-commit-multiple.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.

# reproduce issue2264, issue2516

create test repo
  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > transplant =
  > EOF
  $ hg init repo
  $ cd repo
  $ template="{rev}  {desc|firstline}  [{branch}]\n"

# we need to start out with two changesets on the default branch
# in order to avoid the cute little optimization where transplant
# pulls rather than transplants
add initial changesets
  $ echo feature1 > file1
  $ hg ci -Am"feature 1"
  adding file1
  $ echo feature2 >> file2
  $ hg ci -Am"feature 2"
  adding file2

# The changes to 'bugfix' are enough to show the bug: in fact, with only
# those changes, it's a very noisy crash ("RuntimeError: nothing
# committed after transplant").  But if we modify a second file in the
# transplanted changesets, the bug is much more subtle: transplant
# silently drops the second change to 'bugfix' on the floor, and we only
# see it when we run 'hg status' after transplanting.  Subtle data loss
# bugs are worse than crashes, so reproduce the subtle case here.
commit bug fixes on bug fix branch
  $ hg branch fixes
  marked working directory as branch fixes
  (branches are permanent and global, did you want a bookmark?)
  $ echo fix1 > bugfix
  $ echo fix1 >> file1
  $ hg ci -Am"fix 1"
  adding bugfix
  $ echo fix2 > bugfix
  $ echo fix2 >> file1
  $ hg ci -Am"fix 2"
  $ hg log -G --template="$template"
  @  3  fix 2  [fixes]
  |
  o  2  fix 1  [fixes]
  |
  o  1  feature 2  [default]
  |
  o  0  feature 1  [default]
  
transplant bug fixes onto release branch
  $ hg update 0
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg branch release
  marked working directory as branch release
  $ hg transplant 2 3
  applying [0-9a-f]{12} (re)
  [0-9a-f]{12} transplanted to [0-9a-f]{12} (re)
  applying [0-9a-f]{12} (re)
  [0-9a-f]{12} transplanted to [0-9a-f]{12} (re)
  $ hg log -G --template="$template"
  @  5  fix 2  [release]
  |
  o  4  fix 1  [release]
  |
  | o  3  fix 2  [fixes]
  | |
  | o  2  fix 1  [fixes]
  | |
  | o  1  feature 2  [default]
  |/
  o  0  feature 1  [default]
  
  $ hg status
  $ hg status --rev 0:4
  M file1
  A bugfix
  $ hg status --rev 4:5
  M bugfix
  M file1

now test that we fixed the bug for all scripts/extensions
  $ cat > $TESTTMP/committwice.py <<__EOF__
  > from mercurial import ui, hg, match, node
  > from time import sleep
  > 
  > def replacebyte(fn, b):
  >     f = open(fn, "rb+")
  >     f.seek(0, 0)
  >     f.write(b)
  >     f.close()
  > 
  > def printfiles(repo, rev):
  >     print "revision %s files: %s" % (rev, repo[rev].files())
  > 
  > repo = hg.repository(ui.ui.load(), '.')
  > assert len(repo) == 6, \
  >        "initial: len(repo): %d, expected: 6" % len(repo)
  > 
  > replacebyte("bugfix", "u")
  > sleep(2)
  > try:
  >     print "PRE: len(repo): %d" % len(repo)
  >     wlock = repo.wlock()
  >     lock = repo.lock()
  >     replacebyte("file1", "x")
  >     repo.commit(text="x", user="test", date=(0, 0))
  >     replacebyte("file1", "y")
  >     repo.commit(text="y", user="test", date=(0, 0))
  >     print "POST: len(repo): %d" % len(repo)
  > finally:
  >     lock.release()
  >     wlock.release()
  > printfiles(repo, 6)
  > printfiles(repo, 7)
  > __EOF__
  $ $PYTHON $TESTTMP/committwice.py
  PRE: len(repo): 6
  POST: len(repo): 8
  revision 6 files: ['bugfix', 'file1']
  revision 7 files: ['file1']

Do a size-preserving modification outside of that process
  $ echo abcd > bugfix
  $ hg status
  M bugfix
  $ hg log --template "{rev}  {desc}  {files}\n" -r5:
  5  fix 2  bugfix file1
  6  x  bugfix file1
  7  y  file1

  $ cd ..