[PATCH v5 0/3] rev-list: add support for commits in `--missing`

The `--missing` option in git-rev-list(1) was introduced intitally to deal with missing blobs in the context of promissory notes. Eventually the option was extended to also support tree objects in 7c0fe330d5 (rev-list: handle missing tree objects properly,2018-10-05).

This patch series extends the `--missing` option to also add support for commit objects. We do this by introducing a new flag `MISSING` which is added whenever we encounter a missing commit during traversal. Then in `builtin/rev-list` we check for this flag and take the appropriate action based on the `--missing=*` option used.

This series is an alternate to the patch series I had posted earlier: https://lore.kernel.org/git/20230908174208.249184-1-karthik.188@gmail.com/. In that patch, we introduced an option `--ignore-missing-links` which was added to expose the `ignore_missing_links` bit to the user. The issue in that patch was that, the option `--ignore-missing-links` didn't play well the pre-existing `--missing` option. This series avoids that route and just extends the `--missing` option for commits to solve the same problem.

V4 of the series can be found here: https://lore.kernel.org/git/20231024122631.158415-1-karthik.188@gmail.com/T/#ma7f07bc637e20e2a9558b23e8081957af61f63ce

Changes from v4:
- Rename `missing_objects` to `missing_commits` since we only deal
with commits.
- Fix incorrect indentation
- clear oidset after traversal in `release_revisions()` 

Range diff:

1:  8c469cf479 = 1:  8c469cf479 revision: rename bit to `do_not_die_on_missing_objects`
2:  76ce43d973 = 2:  76ce43d973 rev-list: move `show_commit()` to the bottom
3:  d892f0b82d ! 3:  6f0c74f888 rev-list: add commit object support in `--missing` option
    @@ Commit message
         between the main and alternate object directory.
     
         Helped-by: Patrick Steinhardt <ps@pks.im>
    +    Helped-by: Junio C Hamano <gitster@pobox.com>
         Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
     
      ## builtin/rev-list.c ##
    @@ builtin/rev-list.c: static void show_commit(struct commit *commit, void *data)
      	display_progress(progress, ++progress_counter);
      
     +	if (revs->do_not_die_on_missing_objects &&
    -+	    oidset_contains(&revs->missing_objects, &commit->object.oid)) {
    ++	    oidset_contains(&revs->missing_commits, &commit->object.oid)) {
     +		finish_object__ma(&commit->object);
     +		return;
     +	}
    @@ list-objects.c: static void do_traverse(struct traversal_context *ctx)
      		if (!ctx->revs->tree_objects)
      			; /* do not bother loading tree */
     +		else if (ctx->revs->do_not_die_on_missing_objects &&
    -+			 oidset_contains(&ctx->revs->missing_objects, &commit->object.oid))
    ++			 oidset_contains(&ctx->revs->missing_commits, &commit->object.oid))
     +			;
      		else if (repo_get_commit_tree(the_repository, commit)) {
      			struct tree *tree = repo_get_commit_tree(the_repository,
    @@ revision.c: static int process_parents(struct rev_info *revs, struct commit *com
      	if (commit->object.flags & ADDED)
      		return 0;
     +	if (revs->do_not_die_on_missing_objects &&
    -+		oidset_contains(&revs->missing_objects, &commit->object.oid))
    ++	    oidset_contains(&revs->missing_commits, &commit->object.oid))
     +		return 0;
      	commit->object.flags |= ADDED;
      
    @@ revision.c: static int process_parents(struct rev_info *revs, struct commit *com
      			}
     -			return -1;
     +
    -+			if (!revs->do_not_die_on_missing_objects)
    -+				return -1;
    ++			if (revs->do_not_die_on_missing_objects)
    ++				oidset_insert(&revs->missing_commits, &p->object.oid);
     +			else
    -+				oidset_insert(&revs->missing_objects, &p->object.oid);
    ++				return -1; /* corrupt repository */
      		}
      		if (revs->sources) {
      			char **slot = revision_sources_at(revs->sources, p);
    +@@ revision.c: void release_revisions(struct rev_info *revs)
    + 	clear_decoration(&revs->merge_simplification, free);
    + 	clear_decoration(&revs->treesame, free);
    + 	line_log_free(revs);
    ++	oidset_clear(&revs->missing_commits);
    + }
    + 
    + static void add_child(struct rev_info *revs, struct commit *parent, struct commit *child)
     @@ revision.c: int prepare_revision_walk(struct rev_info *revs)
      				       FOR_EACH_OBJECT_PROMISOR_ONLY);
      	}
      
     +	if (revs->do_not_die_on_missing_objects)
    -+		oidset_init(&revs->missing_objects, 0);
    ++		oidset_init(&revs->missing_commits, 0);
     +
      	if (!revs->reflog_info)
      		prepare_to_use_bloom_filter(revs);
    @@ revision.h: struct rev_info {
      	/* Location where temporary objects for remerge-diff are written. */
      	struct tmp_objdir *remerge_objdir;
     +
    -+	/* Missing objects to be tracked without failing traversal. */
    -+	struct oidset missing_objects;
    ++	/* Missing commits to be tracked without failing traversal. */
    ++	struct oidset missing_commits;
      };
      
      /**

Karthik Nayak (3):
  revision: rename bit to `do_not_die_on_missing_objects`
  rev-list: move `show_commit()` to the bottom
  rev-list: add commit object support in `--missing` option

 builtin/reflog.c            |  2 +-
 builtin/rev-list.c          | 93 +++++++++++++++++++------------------
 list-objects.c              |  5 +-
 revision.c                  | 17 ++++++-
 revision.h                  | 21 +++++----
 t/t6022-rev-list-missing.sh | 74 +++++++++++++++++++++++++++++
 6 files changed, 156 insertions(+), 56 deletions(-)
 create mode 100755 t/t6022-rev-list-missing.sh