On Mon, Apr 05, 2021 at 11:48:56AM -0700, Junio C Hamano wrote:

Derrick Stolee [off-list ref] writes:

quoted

... but it becomes difficult
when we intend to make a distinction between "refs/heads/" and
other sub-areas within "refs/". Finally, I punted on that
conversion and made the logic in 'prefetch' extremely obvious:

1. If the refspec's 'dst' starts with "refs/", then replace
   that prefix with "refs/prefetch/".

2. If the refspec's 'dst' does not start with "refs/", then
   concatenate "refs/prefetch/" and 'dst'.

This will keep a roughly-equivalent partition of refs (some
might have previously collided that will not any more).

Makes sense.  Do we need to add another rule?

3. If the refspec does not have 'dst', ignore it.

I just tried what I think you're saying here.

Consider this fetch config:

$ git config --local --get-regexp "pr-924"
remote.pr-924.url https://github.com/gitgitgadget/git
remote.pr-924.fetch +refs/tags/pr-924/derrickstolee/maintenance/refspec-v1

Seems legal, fetch even works

$ git fetch pr-924
Fetching pr-924
From https://github.com/gitgitgadget/git
 * tag                         pr-924/derrickstolee/maintenance/refspec-v1 -> FETCH_HEAD


Prefetch segfaults

$ git maintenance run --task prefetch
[1]    3811315 segmentation fault (core dumped)  git maintenance run --task prefetch


refspec which isn't a 'negative' with a src, but no dst.


Quick hack:

diff --git a/builtin/gc.c b/builtin/gc.c
index 92cb8b4e0bfa..2f4b8f2375c3 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c

@@ -899,6 +899,10 @@ static int fetch_remote(struct remote *remote, void *cbdata)
                        continue;
                }

+               if (!rsi->dst) {
+                       continue;
+               }
+
                refspec_item_init(&replace, remote->fetch.raw[i], 1);

                /*

Better, but now a different issue:

$ git maintenance run --task prefetch
fatal: --refmap option is only meaningful with command-line refspec(s).
error: failed to prefetch remotes
error: task 'prefetch' failed

So a "remote" where the only fetch url is skipped.

quoted

I have posted my patch series [1], so please take a look. It
builds up the infrastructure to properly test such a refspec
expansion, if we wish to do so.

[1] https://lore.kernel.org/git/pull.924.git.1617627856.gitgitgadget@gmail.com/ (local)

Thanks,
-Stolee

Thanks.