tests/test-largefiles-small-disk.t

clfilter: fallback to unfiltered version when linkrev point to filtered history


On `filectx`, linkrev may point to any revision in the repository. When the
repository is filtered this may lead to `filectx` trying to build `changectx`
for filtered revision. In such case we fallback to creating `changectx` on the
unfiltered version of the reposition. This fallback should not be an issue
because `changectx` from `filectx` are not used in complex operation that
care about filtering. It is complicated to work around the issue in a
clearer way as code raising such `filectx` rarely have access to the
repository directly.

Linkrevs create a lot of issue with filtering. It is stored in revlog entry at
creation time and never changed. Nothing prevent the changeset revision pointed
to become filtered. Several bogus behavior emerge from such situation. Those
bugs are complex to solve and not part of the current effort to install
filtering. This changeset is simple hack that prevent plain crash in favor on
minor misbehavior without visible effect.

This "hack" is longly documented in to code itself to help people that would
look at it in the future.

Test how largefiles abort in case the disk runs full

  $ cat > criple.py <<EOF
  > import os, errno, shutil
  > from mercurial import util
  > #
  > # this makes the original largefiles code abort:
  > def copyfileobj(fsrc, fdst, length=16*1024):
  >     fdst.write(fsrc.read(4))
  >     raise IOError(errno.ENOSPC, os.strerror(errno.ENOSPC))
  > shutil.copyfileobj = copyfileobj
  > #
  > # this makes the rewritten code abort:
  > def filechunkiter(f, size=65536, limit=None):
  >     yield f.read(4)
  >     raise IOError(errno.ENOSPC, os.strerror(errno.ENOSPC))
  > util.filechunkiter = filechunkiter
  > #
  > def oslink(src, dest):
  >     raise OSError("no hardlinks, try copying instead")
  > util.oslink = oslink
  > EOF

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "largefiles =" >> $HGRCPATH

  $ hg init alice
  $ cd alice
  $ echo "this is a very big file" > big
  $ hg add --large big
  $ hg commit --config extensions.criple=$TESTTMP/criple.py -m big
  abort: No space left on device
  [255]

The largefile is not created in .hg/largefiles:

  $ ls .hg/largefiles
  dirstate

The user cache is not even created:

  >>> import os; os.path.exists("$HOME/.cache/largefiles/")
  False

Make the commit with space on the device:

  $ hg commit -m big

Now make a clone with a full disk, and make sure lfutil.link function
makes copies instead of hardlinks:

  $ cd ..
  $ hg --config extensions.criple=$TESTTMP/criple.py clone --pull alice bob
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  getting changed largefiles
  abort: No space left on device
  [255]

The largefile is not created in .hg/largefiles:

  $ ls bob/.hg/largefiles