car get-dag gives no decoder registered for multicodec code 120 (0x78)

[Warbo]

I can't seem to extract git-raw DAGs.

For example, if we add a Git repo to Kubo:

$ git init --quiet
$ mkdir -p foo/bar
$ echo hello > foo/bar/baz
$ git add foo/bar/baz 
$ git commit -m "Hi"
[master (root-commit) 4a8cc80] Hi
 1 file changed, 1 insertion(+)
 create mode 100644 foo/bar/baz
$ echo goodbye > foo/bar/baz 
$ git add foo/bar/baz 
$ git commit -m "Bye"
[master 1c641f7] Bye
 1 file changed, 1 insertion(+), 1 deletion(-)
$ ls .git/objects/*/*
.git/objects/05/4e3e01c75de2975d1bb6e436254ecf988e650f
.git/objects/1c/641f7df8a69a99c0bb1b1a1606ff1b650c6785
.git/objects/1f/72a0a3ba198abc778252eaee11142ce80244cc
.git/objects/25/42a3b2478a94f6dd2dae1a156e618a9d8bcda8
.git/objects/4a/8cc80560cf1a1a702f7bae8ec4c37aa8de9f2b
.git/objects/53/6bdc2d8a69bddedc4472fbdb3ee346d2b230a3
.git/objects/53/9ced6ac21a843e2ff88e3dc79e6ffb6dda2cc9
.git/objects/9e/0a88cb754f425b52a72ceffa96cd758c1a53ab
.git/objects/ce/013625030ba8dba906f756967f9e9ca394464a
.git/objects/dd/7e1c6f0fefe118f0b63d9f10908c460aa317a6
$ for OBJ in .git/objects/*/*; do < "$OBJ" zlib-flate -uncompress | ipfs block put --cid-codec git-raw --mhtype sha1; done
baf4bcfafjy7adr254klv2g5w4q3cktwptchgkdy
baf4bcfa4mqpx36fgtkm4boy3dilan7y3muggpbi
baf4bcfa7okqkhoqzrk6hpass5lxbcfbm5abejta
baf4bcfbfikr3er4kst3n2lnodikw4ymktwf43ka
baf4bcfckrteakygpdinhal33v2hmjq32vdpj6ky
baf4bcfctnpoc3ctjxxpnyrds7pnt5y2g2kzdbiy
baf4bcfctttwwvqq2qq7c76eohxdz4373nxnczsi
baf4bcfe6bkemw5kpijnvfjzm575jntlvrqnfhky
baf4bcfgoae3ckaylvdn2sbxxk2lh7hu4uokemsq
baf4bcfg5pyog6d7p4empbnr5t4ijbdcgbkrrpjq

Then make a CAR for the HEAD commit (this will include ancestors, trees and blobs thanks to the git-raw codec):

$ ipfs dag export "$(printf 'f01781114%s' "$(git rev-parse HEAD)")" > HEAD.car
 0s  986 B / ? [---------------------------=-------------------------------------------------] 54.57 KiB/s 0s 
$ car inspect HEAD.car
Version: 1
Roots: baf4bcfa4mqpx36fgtkm4boy3dilan7y3muggpbi
Root blocks present in data: Yes
Block count: 10
Min / average / max block length (bytes): 13 / 68 / 239
Min / average / max CID length (bytes): 24 / 24 / 24
Block count per codec:
	git-raw: 10
CID count per multihash:
	sha1: 10

car inspect seems happy. Now let's say we want to make a smaller CAR with just the latest tree, ignoring all the history and commit info:

$ car get-dag HEAD.car "$(printf 'f01781114%s' "$(git rev-parse HEAD^{tree})")" > TREE.car

2025/03/12 00:52:58 could not choose a decoder: no decoder registered for multicodec code 120 (0x78)

It seems like the git-raw multicodec isn't supported, and I couldn't find any run-time or compile-time options to adjust the supported codecs (though I might have missed it, since I'm not familiar with Go).

[rvagg]

I think https://github.com/ipfs/go-ipld-git should be compatible enough with the interfaces here to just pull in. If you want to contribute this you could open a PR to:

go get github.com/ipfs/go-ipld-git

Then put _ "github.com/ipfs/go-ipld-git" near the top of the file @

go-car/cmd/car/get.go

Lines 13 to 17 in 291de5e

	_ "github.com/ipld/go-ipld-prime/codec/cbor"
	_ "github.com/ipld/go-ipld-prime/codec/dagcbor"
	_ "github.com/ipld/go-ipld-prime/codec/dagjson"
	_ "github.com/ipld/go-ipld-prime/codec/json"
	_ "github.com/ipld/go-ipld-prime/codec/raw"

Then it should work 🤞 .