From: Johannes Schindelin <johannes.schindelin@xxxxxx>
When `git fetch --update-shallow` needs to test for commit ancestry, it
can naturally run into a missing object (e.g. if it is a parent of a
shallow commit). To accommodate, the merge base logic will need to be
able to handle this situation gracefully.
Currently, that logic pretends that a missing parent commit is
equivalent to a missing parent commit, and for the purpose of
`--update-shallow` that is exactly what we need it to do.
Therefore, let's introduce a flag to indicate when that is precisely the
logic we want.
We need a flag, and cannot rely on `is_repository_shallow()` to indicate
that situation, because that function would return 0: There may not
actually be a `shallow` file, as demonstrated e.g. by t5537.10 ("add new
shallow root with receive.updateshallow on") and t5538.4 ("add new
shallow root with receive.updateshallow on").
Note: shallow commits' parents are set to `NULL` internally already,
therefore there is no need to special-case shallow repositories here, as
the merge-base logic will not try to access parent commits of shallow
commits.
Likewise, partial clones aren't an issue either: If a commit is missing
during the revision walk in the merge-base logic, it is fetched via
`promisor_remote_get_direct()`. And not only the single missing commit
object: Due to the way the "promised" objects are fetched (in
`fetch_objects()` in `promisor-remote.c`, using `fetch
--filter=blob:none`), there is no actual way to fetch a single commit
object, as the remote side will pass that commit OID to `pack-objects
--revs [...]` which in turn passes it to `rev-list` which interprets
this as a commit _range_ instead of a single object. Therefore, in
partial clones (unless they are shallow in addition), all commits
reachable from a commit that is in the local object database are also
present in that local database.
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
commit-reach.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/commit-reach.c b/commit-reach.c
index 5ff71d72d51..7112b10eeea 100644
--- a/commit-reach.c
+++ b/commit-reach.c
@@ -53,7 +53,8 @@ static int queue_has_nonstale(struct prio_queue *queue)
static struct commit_list *paint_down_to_common(struct repository *r,
struct commit *one, int n,
struct commit **twos,
- timestamp_t min_generation)
+ timestamp_t min_generation,
+ int ignore_missing_commits)
{
struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
struct commit_list *result = NULL;
@@ -108,6 +109,13 @@ static struct commit_list *paint_down_to_common(struct repository *r,
if (repo_parse_commit(r, p)) {
clear_prio_queue(&queue);
free_commit_list(result);
+ /*
+ * At this stage, we know that the commit is
+ * missing: `repo_parse_commit()` uses
+ * `OBJECT_INFO_DIE_IF_CORRUPT` and therefore
+ * corrupt commits would already have been
+ * dispatched with a `die()`.
+ */
return NULL;
}
p->object.flags |= flags;
@@ -143,7 +151,7 @@ static struct commit_list *merge_bases_many(struct repository *r,
return NULL;
}
- list = paint_down_to_common(r, one, n, twos, 0);
+ list = paint_down_to_common(r, one, n, twos, 0, 0);
while (list) {
struct commit *commit = pop_commit(&list);
@@ -214,7 +222,7 @@ static int remove_redundant_no_gen(struct repository *r,
min_generation = curr_generation;
}
common = paint_down_to_common(r, array[i], filled,
- work, min_generation);
+ work, min_generation, 0);
if (array[i]->object.flags & PARENT2)
redundant[i] = 1;
for (j = 0; j < filled; j++)
@@ -504,7 +512,7 @@ int repo_in_merge_bases_many(struct repository *r, struct commit *commit,
bases = paint_down_to_common(r, commit,
nr_reference, reference,
- generation);
+ generation, ignore_missing_commits);
if (commit->object.flags & PARENT2)
ret = 1;
clear_commit_marks(commit, all_flags);
--
gitgitgadget
