Largefiles allows for tracking large, incompressible binary files in Mercurial
without requiring excessive bandwidth for clones and pulls.  Files added as
largefiles are not tracked directly by Mercurial; rather, their revisions are
identified by a checksum, and Mercurial tracks these checksums.  This way, when
you clone a repository or pull in changesets, the large files in older
revisions of the repository are not needed, and only the ones needed to update
to the current version are downloaded.  This saves both disk space and
bandwidth.

If you are starting a new repository or adding new large binary files, using
largefiles for them is as easy as adding '--large' to your hg add command.  For
example:

$ dd if=/dev/urandom of=thisfileislarge count=2000
$ hg add --large thisfileislarge
$ hg commit -m 'add thisfileislarge, which is large, as a largefile'

When you push a changeset that affects largefiles to a remote repository, its
largefile revisions will be uploaded along with it.  Note that the remote
Mercurial must also have the largefiles extension enabled for this to work.

When you pull a changeset that affects largefiles from a remote repository,
nothing different from Mercurial's normal behavior happens.  However, when you
update to such a revision, any largefiles needed by that revision are
downloaded and cached if they have never been downloaded before.  This means
that network access is required to update to revision you have not yet updated
to.

If you already have large files tracked by Mercurial without the largefiles
extension, you will need to convert your repository in order to benefit from
largefiles.  This is done with the 'hg lfconvert' command:

$ hg lfconvert --size 10 oldrepo newrepo

By default, in repositories that already have largefiles in them, any new file
over 10MB will automatically be added as largefiles.  To change this
threshhold, set [largefiles].size in your Mercurial config file to the minimum
size in megabytes to track as a largefile, or use the --lfsize option to the
add command (also in megabytes):

[largefiles]
size = 2

$ hg add --lfsize 2

The [largefiles].patterns config option allows you to specify specific
space-separated filename patterns (in shell glob syntax) that should always be
tracked as largefiles:

[largefiles]
pattens = *.jpg *.{png,bmp} library.zip content/audio/*