Shallow clones with explicit history cutoff?

Hi,

use case: I am packaging the FOO program for Debian. FOO is maintained in git but it has a bunch of problems (e.g. because somebody mistakenly checked in a huge blob which would give the ).

The current workflow for this is to create a new branch, remove the offending bits if necessary, create a FOO-clean.tar.xz file, and ship that as "original source". I find that to be suboptimal.

What I would like to have, instead, is a version of shallow cloning which cuts off not at a pre-determined depth, but at a given branch (or set of branches). In other words, given

            +-J--K  (packaged)
           /    /
  +-F--G--H----I    (clean)
 /       /
A---B---C---D---E   (upstream)

a command "git clone --shallow-until upstream $REPO" (or however that would be named) would create a shallow git archive which contains branches packaged+clean, with commits FGHIJK. In contrast, with --single-branch and --depth 4 I would get CGHIJK, which isn't what I'd want.

As I have not spent too much time with the git sources lately (as in "None at all"), some pointers where to start implementing this would be appreciated, assuming (a) this has a reasonable chance of landing in git and (b) nobody beats me to it. ;-)

On Thu, Aug 21, 2014 at 10:39 PM, Matthias Urlichs <matthias@urlichs.de> wrote:

I would imagine a more generic mechanism "git clone --shallow-rev=<rev> $REPO" where you could pass anything that "git rev-list" can accept (maybe more restricted, and some verification required). --shallow-rev could be repeated. So in your case it could be "git clone --shallow-rev="^A" $REPO". We could even maybe turn --depth into a generic thing that is accepted by rev-list so that it could be easily combined with other rev-list options (--shallow-rev and --depth are mutually exclusive).

I'd like to see this implemented. You are not the first one complaining about the (lack of) flexibility of --depth. If you have time, I may be able to support (I should not take on another topic given my many ongoing/unfinished topics). The starting point is upload-pack.c. And GIT_TRACE env variable will be your friend. Search for get_shallow_commits(). There the function is supposed to traverse down from want_obj and set/unset SHALLOW/NOT_SHALLOW flags properly.

SHALLOW flag should be set right before the cut-out commit (e.g. B and F if you want to cut A out). NOT_SHALLOW flags could be used to remove shallow lines in the receiver repo. If you traverse past an existing shallow point in the client (this is the fetch/pull case, not clone), then you should set NOT_SHALLOW so the client knows to remove that point from their $GIT_DIR/shallow. Once you set these properly, the rest should work.

Hi,

Duy Nguyen:

Umm, no. ^E (or ^upstream) would do what I want. Hopefully. ;-)

But you're right, that would fit far better into the existing git paradigms.

Welcome to the club. :-/

Thanks for the pointers. I'll see what I can do (and when).