Re: [PATCH] remote: prefer exact matches when using refspecs
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Jul 31, 2018, 21:53 UTC
- Message-ID
- <xmqq600v9imy.fsf@gitster-ct.c.googlers.com>
- In-Reply-To
- <20180731211832.142014-1-jonathantanmy@google.com>
Jonathan Tan <jonathantanmy@google.com> writes:
> When matching a non-wildcard LHS of a refspec against a list of refs, > find_ref_by_name_abbrev() returns the first ref that matches using the > DWIM rules used by refname_match() in refs.c, even if an exact match > occurs later in the list of refs.
When you have refs/heads/refs/heads/s and refs/heads/s, and if you ask for refs/heads/s, you want that exact match (i.e. the latter) to take precedence over DWIMmed refs/heads/refs/heads/s.
What is unfortunate is that ref_rev_parse_rules[] array already expresses that preference by listing the "fullname" choice "%.*s" before other DWIM choices like "refs/heads/%.*s".
Now we iterate over refs we say from ls-remote output, and with the updated one, the logic _manually_ gives the precedence to the first entry in ref_rev_parse_rules[], so in that "I have a branch s and also another branch refs/heads/s" case, that may happen to work, but would the updated code do the right thing when you have entries that can match, say, both second and third entry in the rules[] and tiebreak correctly the same way? Say you ask for "tags/T" when there are "refs/tags/T" and "refs/heads/tags/T" at the same time in the refs linked list. None of the ref on refs list trigger !strcmp() as there is no exact mqatch, and refname_match() would say "Yeah I see a match" when checking "refs/heads/tags/T" and say it is the best match. Then it finds "refs/tags/T" also on the refs list and finds it also matches user-supplied "tags/T".
In order to resolve this correctly with the precedence rules, I think you need to make refname_match() return the precedence number (e.g. give 1 to "%.*s", 2 to "refs/%.*s", etc., using the index in ref_rev_parse_rules[] array), and make this loop keep track of the "best" match paying attention to the returned precedence.
Show 77 quoted lines
> This causes unexpected behavior when (for example) fetching using the
> refspec "refs/heads/s:<something>" from a remote with both
> "refs/heads/refs/heads/s" and "refs/heads/s". (Even if the former was
> inadvertently created, one would still expect the latter to be fetched.)
>
> This problem has only been observed when the desired ref comes after the
> undesired ref in alphabetical order. However, for completeness, the test
> in this patch also checks what happens when the desired ref comes first
> alphabetically.
>
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
> remote.c | 7 +++++--
> t/t5510-fetch.sh | 28 ++++++++++++++++++++++++++++
> 2 files changed, 33 insertions(+), 2 deletions(-)
>
> diff --git a/remote.c b/remote.c
> index 3fd43453f..eeffe3488 100644
> --- a/remote.c
> +++ b/remote.c
> @@ -1687,12 +1687,15 @@ static struct ref *get_expanded_map(const struct ref *remote_refs,
>
> static const struct ref *find_ref_by_name_abbrev(const struct ref *refs, const char *name)
> {
> + const struct ref *best_match = NULL;
> const struct ref *ref;
> for (ref = refs; ref; ref = ref->next) {
> - if (refname_match(name, ref->name))
> + if (!strcmp(name, ref->name))
> return ref;
> + if (refname_match(name, ref->name))
> + best_match = ref;
> }
> - return NULL;
> + return best_match;
> }
>
> struct ref *get_remote_ref(const struct ref *remote_refs, const char *name)
> diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
> index e402aee6a..da88f35f0 100755
> --- a/t/t5510-fetch.sh
> +++ b/t/t5510-fetch.sh
> @@ -535,6 +535,34 @@ test_expect_success "should be able to fetch with duplicate refspecs" '
> )
> '
>
> +test_expect_success 'LHS of refspec prefers exact matches' '
> + mkdir lhs-exact &&
> + (
> + cd lhs-exact &&
> + git init server &&
> + test_commit -C server unwanted &&
> + test_commit -C server wanted &&
> +
> + git init client &&
> +
> + # Check a name coming after "refs" alphabetically ...
> + git -C server update-ref refs/heads/s wanted &&
> + git -C server update-ref refs/heads/refs/heads/s unwanted &&
> + git -C client fetch ../server refs/heads/s:refs/heads/checkthis &&
> + git -C server rev-parse wanted >expect &&
> + git -C client rev-parse checkthis >actual &&
> + test_cmp expect actual &&
> +
> + # ... and one before.
> + git -C server update-ref refs/heads/q wanted &&
> + git -C server update-ref refs/heads/refs/heads/q unwanted &&
> + git -C client fetch ../server refs/heads/q:refs/heads/checkthis &&
> + git -C server rev-parse wanted >expect &&
> + git -C client rev-parse checkthis >actual &&
> + test_cmp expect actual
> + )
> +'
> +
> # configured prune tests
>
> set_config_tristate () {