radicle-surf: Repository.blob_at() to retrieve a blob using its oid.

[keepsimple1]

This is motived by a discussion on zulip.

[keepsimple1]

The input commit is not required if we only wanted to retrieve the blob content. It is here as we also need to retrieve the Blob.commit that created the blob (oid).

[FintanH]

I wasn't expecting to have the commit as a parameter, so what if we changed the result type to just BlobRef<'a>?

[keepsimple1]

I thought about it, and I chose to have the commit parameter for a couple of reasons:

1. To be consistent in the API (similar to blob()), including the return type Blob. The intent of Blob.commit was helping the caller to identify the last_commit easily without having to do another HTTP call. That is the same for both blob() and blob_at().

2. From the zulip discussion linked in Description, the caller would (most likely) have the commit info available.

[FintanH]

From the zulip discussion linked in Description, the caller would (most likely) have the commit info available.

My reading of the discussion was that we should be able to get a blob without the commit[0]. So if something doesn't know about a commit but does have a blob id, then it can just retrieve the blob content.

[keepsimple1]

I was referring to the original request message.

Yeah, like we discussed so far, there are two options that I can see:

a) Get the blob content only (input: Oid). If the caller wanted to find the commit that created the blob, they make another HTTP call. This is not consistent with existing blob() method.

b) Get the blob content and the commit that created the blob. (input: Oid and a Commit that has the blob. ) . Both info are retrieved in one call. This is consistent with existing blob() method.

For the blob content part, b) does more involved work than a), because it also retrieves the commit.

It's a trade-off. My preference is to go with option b) based on the reasons I mentioned earlier. And if we did want to go with a), I would suggest to re-visit Blob struct and see if it makes sense to separate Blob.commit out, and then change blob() to be consistent with blob_at().

[FintanH]

I was referring to the original request message.

Sure and within that thread, I mentioned how I imagined the URL being '.../blob/<oid>' :)

I don't mind going down this route, but I don't understand why we have to go fetch the commit that created the blob. Can you explain why that's necessary?

I'd expect that we just check the Blob's Oid exists with the Commit's tree, either via diff or using a tree walk.

[keepsimple1]

I don't mind going down this route, but I don't understand why we have to go fetch the commit that created the blob. Can you explain why that's necessary?

It's because this existing Blob struct and its API:

radicle-git/radicle-surf/src/blob.rs

Lines 52 to 54 in 6de53f7

	/// Returns the commit that created this blob.
	pub fn commit(&self) -> &Commit {
	&self.commit