Subject: [PATCH v3 0/4] Beginning of new merge strategy: New API, empty implementation

From: "Elijah Newren via GitGitGadget" <[email-masked]>
Date: Tue, 27 Oct 2020 02:08:06 +0000

In this series, I show the new merge API I have developed in merge-ort, and
show how it differs from that provided by merge-recursive. I do this in four
steps, each corresponding to a patch.

Changes since v2:

 * Extended comments in struct merge_result and in front of function
   definitions to make API usage clearer; in particular, noting how this
   merge backend differs in not using the index (and only updating it as
   part of merge_switch_to_result()).
 * Drop the other private field of struct merge_result, for now.
 * Rename merge_inmemory_* to merge_incore_*

Elijah Newren (4):
  merge-ort: barebones API of new merge strategy with empty
    implementation
  merge-ort-wrappers: new convience wrappers to mimic the old merge API
  fast-rebase: demonstrate merge-ort's API via temporary/hidden command
  merge,rebase,revert: select ort or recursive by config or environment

 Makefile              |   3 +
 builtin.h             |   1 +
 builtin/fast-rebase.c | 210 ++++++++++++++++++++++++++++++++++++++++++
 builtin/merge.c       |  26 +++++-
 builtin/rebase.c      |   9 +-
 builtin/revert.c      |   2 +
 git.c                 |   1 +
 merge-ort-wrappers.c  |  62 +++++++++++++
 merge-ort-wrappers.h  |  25 +++++
 merge-ort.c           |  52 +++++++++++
 merge-ort.h           |  58 ++++++++++++
 sequencer.c           |  71 +++++++++++---
 12 files changed, 505 insertions(+), 15 deletions(-)
 create mode 100644 builtin/fast-rebase.c
 create mode 100644 merge-ort-wrappers.c
 create mode 100644 merge-ort-wrappers.h
 create mode 100644 merge-ort.c
 create mode 100644 merge-ort.h

base-commit: 69986e19ffcfb9af674ae5180689ab7bbf92ed28
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-895%2Fnewren%2Fort-api-with-empty-implementation-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-895/newren/ort-api-with-empty-implementation-v3
Pull-Request: https://github.com/git/git/pull/895

Range-diff vs v2:

 1:  b9e73975ea ! 1:  3357ea415e merge-ort: barebones API of new merge strategy with empty implementation
     @@ merge-ort.c (new)
      +	die("Not yet implemented");
      +}
      +
     -+void merge_inmemory_nonrecursive(struct merge_options *opt,
     -+				 struct tree *merge_base,
     -+				 struct tree *side1,
     -+				 struct tree *side2,
     -+				 struct merge_result *result)
     ++void merge_incore_nonrecursive(struct merge_options *opt,
     ++			       struct tree *merge_base,
     ++			       struct tree *side1,
     ++			       struct tree *side2,
     ++			       struct merge_result *result)
      +{
      +	die("Not yet implemented");
      +}
      +
     -+void merge_inmemory_recursive(struct merge_options *opt,
     -+			      struct commit_list *merge_bases,
     -+			      struct commit *side1,
     -+			      struct commit *side2,
     -+			      struct merge_result *result)
     ++void merge_incore_recursive(struct merge_options *opt,
     ++			    struct commit_list *merge_bases,
     ++			    struct commit *side1,
     ++			    struct commit *side2,
     ++			    struct merge_result *result)
      +{
      +	die("Not yet implemented");
      +}
     @@ merge-ort.h (new)
      +struct tree;
      +
      +struct merge_result {
     -+	/* whether the merge is clean */
     ++	/* Whether the merge is clean */
      +	int clean;
      +
     -+	/* Result of merge.  If !clean, represents what would go in worktree */
     ++	/*
     ++	 * Result of merge.  If !clean, represents what would go in worktree
     ++	 * (thus possibly including files containing conflict markers).
     ++	 */
      +	struct tree *tree;
      +
      +	/*
      +	 * Additional metadata used by merge_switch_to_result() or future calls
     -+	 * to merge_inmemory_*().  Not for external use.
     ++	 * to merge_incore_*().  Includes data needed to update the index (if
     ++	 * !clean) and to print "CONFLICT" messages.  Not for external use.
      +	 */
      +	void *priv;
     -+	unsigned ate;
      +};
      +
     -+/* rename-detecting three-way merge with recursive ancestor consolidation. */
     -+void merge_inmemory_recursive(struct merge_options *opt,
     -+			      struct commit_list *merge_bases,
     -+			      struct commit *side1,
     -+			      struct commit *side2,
     -+			      struct merge_result *result);
     ++/*
     ++ * rename-detecting three-way merge with recursive ancestor consolidation.
     ++ * working tree and index are untouched.
     ++ */
     ++void merge_incore_recursive(struct merge_options *opt,
     ++			    struct commit_list *merge_bases,
     ++			    struct commit *side1,
     ++			    struct commit *side2,
     ++			    struct merge_result *result);
      +
     -+/* rename-detecting three-way merge, no recursion. */
     -+void merge_inmemory_nonrecursive(struct merge_options *opt,
     -+				 struct tree *merge_base,
     -+				 struct tree *side1,
     -+				 struct tree *side2,
     -+				 struct merge_result *result);
     ++/*
     ++ * rename-detecting three-way merge, no recursion.
     ++ * working tree and index are untouched.
     ++ */
     ++void merge_incore_nonrecursive(struct merge_options *opt,
     ++			       struct tree *merge_base,
     ++			       struct tree *side1,
     ++			       struct tree *side2,
     ++			       struct merge_result *result);
      +
     -+/* Update the working tree and index from head to result after inmemory merge */
     ++/* Update the working tree and index from head to result after incore merge */
      +void merge_switch_to_result(struct merge_options *opt,
      +			    struct tree *head,
      +			    struct merge_result *result,
 2:  a9fff811a2 ! 2:  d7f6a834ab merge-ort-wrappers: new convience wrappers to mimic the old merge API
     @@ merge-ort-wrappers.c (new)
      +	}
      +
      +	memset(&result, 0, sizeof(result));
     -+	merge_inmemory_nonrecursive(opt, merge_base, head, merge, &result);
     ++	merge_incore_nonrecursive(opt, merge_base, head, merge, &result);
      +	merge_switch_to_result(opt, head, &result, 1, 1);
      +
      +	return result.clean;
     @@ merge-ort-wrappers.c (new)
      +		return -1;
      +
      +	memset(&tmp, 0, sizeof(tmp));
     -+	merge_inmemory_recursive(opt, merge_bases, side1, side2, &tmp);
     ++	merge_incore_recursive(opt, merge_bases, side1, side2, &tmp);
      +	merge_switch_to_result(opt, head, &tmp, 1, 1);
      +	*result = NULL;
      +
 3:  f38d140c15 ! 3:  27ad756600 fast-rebase: demonstrate merge-ort's API via temporary/hidden command
     @@ builtin/fast-rebase.c (new)
      +		merge_opt.branch2 = short_commit_name(commit);
      +		merge_opt.ancestor = xstrfmt("parent of %s", merge_opt.branch2);
      +
     -+		merge_inmemory_nonrecursive(&merge_opt,
     -+					    base_tree,
     -+					    result.tree,
     -+					    next_tree,
     -+					    &result);
     ++		merge_incore_nonrecursive(&merge_opt,
     ++					  base_tree,
     ++					  result.tree,
     ++					  next_tree,
     ++					  &result);
      +
      +		free((char*)merge_opt.ancestor);
      +		merge_opt.ancestor = NULL;
 4:  5f6c97b889 ! 4:  0479d59c33 merge,rebase,revert: select ort or recursive by config or environment
     @@ sequencer.c: static int do_recursive_merge(struct repository *r,
      -	strbuf_release(&o.obuf);
      +	if (opts->strategy && !strcmp(opts->strategy, "ort")) {
      +		memset(&result, 0, sizeof(result));
     -+		merge_inmemory_nonrecursive(&o, base_tree, head_tree, next_tree,
     ++		merge_incore_nonrecursive(&o, base_tree, head_tree, next_tree,
      +					    &result);
      +		show_output = !is_rebase_i(opts) || !result.clean;
      +		/*
     @@ sequencer.c: static int do_merge(struct repository *r,
      -	ret = merge_recursive(&o, head_commit, merge_commit, reversed, &i);
      +	if (opts->strategy && !strcmp(opts->strategy, "ort")) {
      +		/*
     -+		 * TODO: Should use merge_inmemory_recursive() and
     ++		 * TODO: Should use merge_incore_recursive() and
      +		 * merge_switch_to_result(), skipping the call to
      +		 * merge_switch_to_result() when we don't actually need to
      +		 * update the index and working copy immediately.

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