[PATCH v2] fetch,fetch-pack: clarify connectivity check error

[Jonathan Tan <jonathantanmy@google.com>]

When the connectivity check after a fetch fails, an error message
"<remote> did not send all necessary objects" is printed. That error
message is printed regardless of the reason of failure: in particular,
that message may be printed if the connectivity check fails because a
local object is missing. (The connectivity check reads local objects too
because it compares the set of objects that the remote claims to send
against the set of objects that our refs directly or indirectly
reference.)

Since it is not necessarily true that the remote did not send all
necessary objects, update the error message to be something that more
correctly reflects the situation.

The updated error message is admittedly vague and one alternative
solution would be to update the revision walking code to be able to more
precisely specify if a bad object is supposed to be available locally or
supposed to have been sent by the remote. That would likely require, in
the revision walking code, to delay parsing any object until all its
children has been parsed, which seems to be a significant undertaking.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
As Junio said in [1], my original v1 code doesn't work when an object is
referenced both by a local object and a remote one. I tried looking into
making it work but it looks difficult.

So here is a patch that just changes the error message to a vaguer but
hopefully more correct one. I wonder what the community thinks of it -
I think it is more correct (and means that we do not need to say "it's
not the remote fault despite what the error message says") but at the
same time, many people are already used to this message (and a search
online reveals several web sites that talk about this).

[1] https://lore.kernel.org/git/xmqqh74upyz3.fsf@gitster.g/
---
 builtin/fetch.c | 2 +-
 fetch-pack.c    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/builtin/fetch.c b/builtin/fetch.c
index ac29c2b1ae..15737ca293 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1133,7 +1133,7 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 
 		rm = ref_map;
 		if (check_connected(iterate_ref_map, &rm, &opt)) {
-			rc = error(_("%s did not send all necessary objects\n"), url);
+			rc = error(_("connectivity check failed after fetching from %s\n"), url);
 			goto abort;
 		}
 	}
diff --git a/fetch-pack.c b/fetch-pack.c
index cb6647d657..91269008cc 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -2021,7 +2021,7 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 		if (args->deepen)
 			opt.is_deepening_fetch = 1;
 		if (check_connected(iterate_ref_map, &iterator, &opt)) {
-			error(_("remote did not send all necessary objects"));
+			error(_("connectivity check failed after fetching from remote"));
 			free_refs(ref_cpy);
 			ref_cpy = NULL;
 			rollback_shallow_file(the_repository, &shallow_lock);
-- 
2.36.1.476.g0c4daa206d-goog