From: Eric Sunshine <sunshine@sunshineco.com>
Date: Tue, 12 May 2015 22:01:10 GMT
Subject: Re: [PATCH 3/3] upload-pack: Optionally allow fetching reachable sha1
Message-ID: <CAPig+cQe3=Y15+RBZCxry7-78kbNL6H0PfdYs=OV_DMifOWxaA@mail.gmail.com>
In-Reply-To: <1431465265-18486-3-git-send-email-fredrik.medley@gmail.com>

On Tue, May 12, 2015 at 5:14 PM, Fredrik Medley
<fredrik.medley@gmail.com> wrote:
> With uploadpack.allowReachableSHA1InWant configuration option set on the
> server side, "git fetch" can make a request with a "want" line that names
> an object that has not been advertised (likely to have been obtained out
> of band or from a submodule pointer). Only objects reachable from the
> branch tips, i.e. the union of advertised branches and branches hidden by
> transfer.hideRefs, will be processed. Note that there is an associated
> cost of having to walk back the hstory to check the reachability.

Mentioned previously[1]: s/hstory/history/

> This feature can be used when obtaining the content of a certain commit,
> for which the sha1 is known, without the need of cloning the whole
> repository, especially if a shallow fetch is used. Useful cases are e.g.
> repositories containing large files in the history, fetching only the
> needed data for a submodule checkout, when sharing a sha1 without telling
> which exact branch it belongs to and in Gerrit, if you think in terms of
> commits instead of change numbers. (The Gerrit case has already been
> solved through allowTipSHA1InWant as every Gerrit change has a ref.)
>
> Signed-off-by: Fredrik Medley <fredrik.medley@gmail.com>
> ---
> diff --git a/Documentation/config.txt b/Documentation/config.txt
> index 2b86fe6..ffc4cf4 100644
> --- a/Documentation/config.txt
> +++ b/Documentation/config.txt
> @@ -2538,6 +2538,12 @@ uploadpack.allowTipSHA1InWant::
>         of a hidden ref (by default, such a request is rejected).
>         see also `uploadpack.hideRefs`.
>
> +uploadpack.allowReachableSHA1InWant::
> +       Allow `upload-pack` to accept a fetch request that asks for an
> +       object that is reachable from any ref tip. However, note that
> +       calculating     object reachability is computationally expensive.

Mentioned previously[1]: s/\s+/ /

> +       Defaults to `false`.
> +
> diff --git a/fetch-pack.c b/fetch-pack.c
> index 77174f9..6c63d8e 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -545,7 +547,7 @@ static void filter_refs(struct fetch_pack_args *args,
>         }
>
>         /* Append unmatched requests to the list */
> -       if (allow_request_with_bare_object_name & ALLOW_TIP) {
> +       if (allow_request_with_bare_object_name & (ALLOW_TIP | ALLOW_REACHABLE)) {

Wrap this in extra parentheses to avoid compilation warnings:

    if ((foo & (bar | baz))) {

>                 for (i = 0; i < nr_sought; i++) {
>                         unsigned char sha1[20];
>

[1]: http://article.gmane.org/gmane.comp.version-control.git/268428