Re: [PATCH v3 2/4] format-patch: add '--base' option to record base tree info

> Helped-by: Junio C Hamano <gitster@pobox.com>
> Helped-by: Wu Fengguang <fengguang.wu@intel.com>
> Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
> ---
>  Documentation/git-format-patch.txt | 25 +++++++++++
>  builtin/log.c                      | 89 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 114 insertions(+)
>
> diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
> index 6821441..067d562 100644
> --- a/Documentation/git-format-patch.txt
> +++ b/Documentation/git-format-patch.txt
> @@ -265,6 +265,31 @@ you can use `--suffix=-patch` to get `0001-description-of-my-change-patch`.
>    Output an all-zero hash in each patch's From header instead
>    of the hash of the commit.
>  
> +--base=<commit>::
> +	Record the base tree information to identify the whole tree
> +	the patch series applies to. For example, the patch submitter
> +	has a commit history of this shape:
> +
> +	---P---X---Y---Z---A---B---C
> +
> +	where "P" is the well-known public commit (e.g. one in Linus's tree),
> +	"X", "Y", "Z" are prerequisite patches in flight, and "A", "B", "C"
> +	are the work being sent out, the submitter could say "git format-patch
> +	--base=P -3 C" (or variants thereof, e.g. with "--cover" or using
> +	"Z..C" instead of "-3 C" to specify the range), and the identifiers
> +	for P, X, Y, Z are appended at the end of the _first_ message (either
> +	the cover letter or the first patch in the series).
> +
> +	For non-linear topology, such as
> +
> +	    ---P---X---A---M---C
> +		\         /
> +		 Y---Z---B
> +
> +	the submitter could also use "git format-patch --base=P -3 C" to generate
> +	patches for A, B and C, and the identifiers for P, X, Y, Z are appended
> +	at the end of the _first_ message.

> diff --git a/builtin/log.c b/builtin/log.c
> index 0d738d6..03cbab0 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -1185,6 +1185,82 @@ static int from_callback(const struct option *opt, const char *arg, int unset)
>  	return 0;
>  }
>  
> +struct base_tree_info {
> +	struct object_id base_commit;
> +	int nr_patch_id, alloc_patch_id;
> +	struct object_id *patch_id;
> +};
> +
> +static void prepare_bases(struct base_tree_info *bases,
> +			  const char *base_commit,
> +			  struct commit **list,
> +			  int total)
> +{
> +	struct commit *base = NULL, *commit;
> +	struct rev_info revs;
> +	struct diff_options diffopt;
> +	struct object_id *patch_id;
> +	unsigned char sha1[20];
> +	int i;
> +
> +	diff_setup(&diffopt);
> +	DIFF_OPT_SET(&diffopt, RECURSIVE);
> +	diff_setup_done(&diffopt);
> +
> +	base = lookup_commit_reference_by_name(base_commit);
> +	if (!base)
> +		die(_("Unknown commit %s"), base_commit);
> +	oidcpy(&bases->base_commit, &base->object.oid);
> +
> +	init_revisions(&revs, NULL);
> +	revs.max_parents = 1;
> +	base->object.flags |= UNINTERESTING;
> +	add_pending_object(&revs, &base->object, "base");
> +	for (i = 0; i < total; i++) {
> +		list[i]->object.flags |= 0;

> +	}
> +
> +	if (prepare_revision_walk(&revs))
> +		die(_("revision walk setup failed"));
> +	/*
> +	 * Traverse the prerequisite commits list,
> +	 * get the patch ids and stuff them in bases structure.
> +	 */
> +	while ((commit = get_revision(&revs)) != NULL) {
> +		if (commit->util)
> +			continue;
> +		if (commit_patch_id(commit, &diffopt, sha1))
> +			die(_("cannot get patch id"));
> +		ALLOC_GROW(bases->patch_id, bases->nr_patch_id + 1, bases->alloc_patch_id);
> +		patch_id = bases->patch_id + bases->nr_patch_id;
> +		hashcpy(patch_id->hash, sha1);

> +		bases->nr_patch_id++;
> +	}
> +}
> +
> +static void print_bases(struct base_tree_info *bases)
> +{
> +	int i;
> +
> +	/* Only do this once, either for the cover or for the first one */
> +	if (is_null_oid(&bases->base_commit))
> +		return;
> +
> +	/* Show the base commit */
> +	printf("base-commit: %s\n", oid_to_hex(&bases->base_commit));
> +
> +	/* Show the prerequisite patches */
> +	for (i = 0; i < bases->nr_patch_id; i++)
> +		printf("prerequisite-patch-id: %s\n", oid_to_hex(&bases->patch_id[i]));