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'

  $ 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 (= cahcing 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 1 changesets with 1 changes to 1 files

  (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

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  getting changed largefiles

  large: Can't get file locally

  (no default or default-push path set in hgrc)

  0 largefiles updated, 0 removed

  $ hg status

  ! large

Update working directory to null: this cleanup .hg/largefiles/dirstate

  $ hg update null

  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

  getting changed largefiles

  0 largefiles updated, 0 removed

Update working directory to tip, again.

  $ hg update

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  getting changed largefiles

  large: Can't get file locally

  (no default or default-push path set in hgrc)

  0 largefiles updated, 0 removed

  $ hg status

  ! large