it will be used by the next patch that adds "--generate-static-delta"
to the commit command.
As part of the patch, update the list of supported "params" in the
documentation.
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
The previous diff algorithm was file tree based, and only looked
at modified files that lived at the same path.
However, components like the Linux kernel have versioned
subdirectories, e.g. /usr/lib/modules/$kver/.../ext4.ko. We want to
be able to detect these "modified renames" so that we can compute
diffs (rollsum, bsdiff).
This does an rsync-style prepared delta basically. On my test data,
it shaves ~6MB of uncompressed data. Not a huge amount, but I expect
this to be more useful for things like binaries which embed data, etc.
There's still some silliness here, but there is now only one opcode
open-splice-and-close, that writes a single chunk from the payload.
This is really all we need for metadata, and small content objects are
also fine with this.
We get some deduplication between content objects by creating a
dictionary for (uid,gid,mode) tuples and xattrs.
This still keeps the operation/payload code in, so we could do
rollsums in a future update easily.
You create these with something like:
ostree static-delta generate --empty --to=master
These will be automatically used during pull if no previous revision
exists in the target repo.
These work very much like the normal static deltas except they
are named just by the "to" revision. I.e:
deltas/94/f7d2dc23759dd21f9bd01e6705a8fdf98f90cad3e0109ba3f6c091c1a3774d
for a from-scratch to 94f7d2dc23759dd21f9bd01e6705a8fdf98f90cad3e0109ba3f6c091c1a3774d delta.
https://bugzilla.gnome.org/show_bug.cgi?id=721799
This has a very basic level of functionality (deltas can be generated,
and applied offline). There is only some stubbed out pull code to
fetch them via HTTP.
But, better to commit this now and improve it from a known starting
point, rather than have it languish in a branch.
Matthew Barnes
Giuseppe Scrivano
Colin Walters
Alexander Larsson