Re: [RFC 0/4] Shallow clones with on-demand fetch

[Jonathan Tan <jonathantanmy@google.com>]

On 03/04/2017 11:18 AM, Mark Thomas wrote:
> I was inspired a bit by Microsoft's announcement of their Git VFS.  I
> saw that people have talked in the past about making git fetch objects
> from remotes as they are needed, and decided to give it a try.

For reference, one such conversation is [1]. (cc-ing Ben Peart also)

> The patch series adds a "--on-demand" option to git clone, which, when
> used in conjunction with the existing shallow clone operations, clones
> the full history of the repository's commits, but only the files that
> would be included in the shallow clone.
>
> When a file that is missing is required, git requests the file on-demand
> from the remote, via a new 'upload-file' service.

A reachability check (of the blob) might be a good idea. The current Git 
implementation already supports fetching a blob (perhaps a bug) but has 
problems with reachability calculations that I tried to fix in [2], but 
found some bugs that weren't easily fixable.

As I said in [2], I think that proper fetching of blobs on demand is a 
prerequisite to any sort of missing object tolerance (like your 
on-demand clones), so I haven't thought much about the topics in the 
rest of your patch set.

[1] <20170113155253.1644-1-benpeart@microsoft.com> (you can search for 
emails by Message ID in online archives like 
https://public-inbox.org/git if you don't already have them)
[2] <cover.1487984670.git.jonathantanmy@google.com>