Add car put-block command

[parkan]

• write counterpart to get-block
• can set root on first block write (optional)

this is handy if you need to package up some blocks from an IPFS node (among other cases); ipfs dag export wants to walk the whole DAG, which doesn't work if you only need a shallow traversal

use like:

ipfs block get $CID1 | car put-block foo.car --set-root --version=2 --codec=dag-pb
ipfs block get $CID2 | car put-block foo.car --version=2 --codec=dag-pb

I tried to match the semantics to how the other write commands work

[willscott]

looks generally reasonable. a couple comments to think about, but no strongly held objection to this

[parkan]

ok, I've addressed the concerns:

• removed binary checkin oopsie (should it be gitignored?)
• v1 cars we do naive/cheap append
• accept --cid param, if passed we parse codec out of that and verify that recomputed value matches; otherwise --codec must be passed

[willscott]

Looks great. since we don't have CI tests over this i want to pull and confirm the test script locally, but will plan to merge later today or tomorrow

[parkan]

the remaining nit is that the original commit should have been titled "Add car put-block...` but I think we can let that slide

[willscott]

Thanks again!

[parkan]

Looks great. since we don't have CI tests over this i want to pull and confirm the test script locally, but will plan to merge later today or tomorrow

BTW I'm not sure what you mean by this, I see my tests running in CI? https://github.com/ipld/go-car/actions/runs/18562918723/job/52916178584#step:13:5723

anyway thanks for merging, will be nice to be able to go install without replaces :)