view tests/test-convert-tagsbranch-topology.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.

#require git

  $ echo "[core]" >> $HOME/.gitconfig
  $ echo "autocrlf = false" >> $HOME/.gitconfig
  $ echo "[core]" >> $HOME/.gitconfig
  $ echo "autocrlf = false" >> $HOME/.gitconfig
  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > convert =
  > [convert]
  > hg.usebranchnames = True
  > hg.tagsbranch = tags-update
  > EOF
  $ GIT_AUTHOR_NAME='test'; export GIT_AUTHOR_NAME
  $ GIT_AUTHOR_EMAIL='[e-mail]'; export GIT_AUTHOR_EMAIL
  $ GIT_AUTHOR_DATE="2007-01-01 00:00:00 +0000"; export GIT_AUTHOR_DATE
  $ GIT_COMMITTER_NAME="$GIT_AUTHOR_NAME"; export GIT_COMMITTER_NAME
  $ GIT_COMMITTER_EMAIL="$GIT_AUTHOR_EMAIL"; export GIT_COMMITTER_EMAIL
  $ GIT_COMMITTER_DATE="$GIT_AUTHOR_DATE"; export GIT_COMMITTER_DATE
  $ count=10
  $ action()
  > {
  >     GIT_AUTHOR_DATE="2007-01-01 00:00:$count +0000"
  >     GIT_COMMITTER_DATE="$GIT_AUTHOR_DATE"
  >     git "$@" >/dev/null 2>/dev/null || echo "git command error"
  >     count=`expr $count + 1`
  > }
  $ glog()
  > {
  >     hg log -G --template '{rev} "{desc|firstline}" files: {files}\n' "$@"
  > }
  $ convertrepo()
  > {
  >     hg convert --datesort git-repo hg-repo
  > }

Build a GIT repo with at least 1 tag

  $ mkdir git-repo
  $ cd git-repo
  $ git init >/dev/null 2>&1
  $ echo a > a
  $ git add a
  $ action commit -m "rev1"
  $ action tag -m "tag1" tag1
  $ cd ..

Convert without tags

  $ hg convert git-repo hg-repo --config convert.skiptags=True
  initializing destination hg-repo repository
  scanning source...
  sorting...
  converting...
  0 rev1
  updating bookmarks
  $ hg -R hg-repo tags
  tip                                0:d98c8ad3a4cf
  $ rm -rf hg-repo

Do a first conversion

  $ convertrepo
  initializing destination hg-repo repository
  scanning source...
  sorting...
  converting...
  0 rev1
  updating tags
  updating bookmarks

Simulate upstream  updates after first conversion

  $ cd git-repo
  $ echo b > a
  $ git add a
  $ action commit -m "rev2"
  $ action tag -m "tag2" tag2
  $ cd ..

Perform an incremental conversion

  $ convertrepo
  scanning source...
  sorting...
  converting...
  0 rev2
  updating tags
  updating bookmarks

Print the log

  $ cd hg-repo
  $ glog
  o  3 "update tags" files: .hgtags
  |
  | o  2 "rev2" files: a
  | |
  o |  1 "update tags" files: .hgtags
   /
  o  0 "rev1" files: a
  

  $ cd ..