Create user cache directory

  $ USERCACHE=`pwd`/cache; export USERCACHE

  $ cat <<EOF >> ${HGRCPATH}

  > [extensions]

  > hgext.largefiles=

  > [largefiles]

  > usercache=${USERCACHE}

  > EOF

  $ mkdir -p ${USERCACHE}

Create source repo, and commit adding largefile.

  $ hg init src

  $ cd src

  $ echo large > large

  $ hg add --large large

  $ hg commit -m 'add largefile'

  $ hg rm large

  $ hg commit -m 'branchhead without largefile' large

  $ hg up -qr 0

  $ rm large

  $ echo "0000000000000000000000000000000000000000" > .hglf/large

  $ hg commit -m 'commit missing file with corrupt standin' large

  abort: large: file not found!

  [255]

  $ hg up -Cqr 0

  $ cd ..

Discard all cached largefiles in USERCACHE

  $ rm -rf ${USERCACHE}

Create mirror repo, and pull from source without largefile:

"pull" is used instead of "clone" for suppression of (1) updating to

tip (= caching largefile from source repo), and (2) recording source

repo as "default" path in .hg/hgrc.

  $ hg init mirror

  $ cd mirror

  $ hg pull ../src

  pulling from ../src

  requesting all changes

  adding changesets

  adding manifests

  adding file changes

  added 2 changesets with 1 changes to 1 files

  new changesets eb85d9124f3f:26c18ce05e4e

  (run 'hg update' to get a working copy)

Update working directory to "tip", which requires largefile("large"),

but there is no cache file for it.  So, hg must treat it as

"missing"(!) file.

  $ hg update -r0

  getting changed largefiles