Subject: [PATCH v2 00/20] fundamentals of merge-ort implementation

From: "Elijah Newren via GitGitGadget" <[email-masked]>
Date: Fri, 04 Dec 2020 20:47:50 +0000

This is actually v4 of this series (the first two rounds depended on topics
that hadn't graduated yet, so I hadn't yet used gitgitgadget for submitting
it). As a reminder, if you need to see the first two rounds before I started
submitting this series with gitgitgadget, you can see them over here: 
https://lore.kernel.org/git/[email-masked]/

Changes since v3:

 * Made the small tweaks suggested by Ævar
 * Fixed an embarrassing tree ordering bug in commit 13; base_name_compare()
   != strcmp() is important.

(Tree ordering bug found due to the fact that merge-ort, including many
patches not yet submitted to this list, is in live use at $DAYJOB.)

Elijah Newren (20):
  merge-ort: setup basic internal data structures
  merge-ort: add some high-level algorithm structure
  merge-ort: port merge_start() from merge-recursive
  merge-ort: use histogram diff
  merge-ort: add an err() function similar to one from merge-recursive
  merge-ort: implement a very basic collect_merge_info()
  merge-ort: avoid repeating fill_tree_descriptor() on the same tree
  merge-ort: compute a few more useful fields for collect_merge_info
  merge-ort: record stage and auxiliary info for every path
  merge-ort: avoid recursing into identical trees
  merge-ort: add a preliminary simple process_entries() implementation
  merge-ort: have process_entries operate in a defined order
  merge-ort: step 1 of tree writing -- record basenames, modes, and oids
  merge-ort: step 2 of tree writing -- function to create tree object
  merge-ort: step 3 of tree writing -- handling subdirectories as we go
  merge-ort: basic outline for merge_switch_to_result()
  merge-ort: add implementation of checkout()
  tree: enable cmp_cache_name_compare() to be used elsewhere
  merge-ort: add implementation of record_conflicted_index_entries()
  merge-ort: free data structures in merge_finalize()

 merge-ort.c | 1221 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 tree.c      |    2 +-
 tree.h      |    2 +
 3 files changed, 1221 insertions(+), 4 deletions(-)

base-commit: e67fbf927dfdf13d0b21dc6ea15dc3c7ef448ea0
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-923%2Fnewren%2Fort-basics-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-923/newren/ort-basics-v2
Pull-Request: https://github.com/git/git/pull/923

Range-diff vs v1:

  1:  2568ec92c6 =  1:  2568ec92c6 merge-ort: setup basic internal data structures
  2:  3a063865c3 !  2:  b658536f59 merge-ort: add some high-level algorithm structure
     @@ merge-ort.c: struct conflict_info {
      +			      struct tree *side1,
      +			      struct tree *side2)
      +{
     ++	/* TODO: Implement this using traverse_trees() */
      +	die("Not yet implemented.");
      +}
      +
  3:  5615f0eecb =  3:  acb40f5c16 merge-ort: port merge_start() from merge-recursive
  4:  564b072ac1 =  4:  22fecf6ccd merge-ort: use histogram diff
  5:  91516799e4 !  5:  6c4c0c15b3 merge-ort: add an err() function similar to one from merge-recursive
     @@ merge-ort.c: struct conflict_info {
       			      struct tree *side1,
       			      struct tree *side2)
       {
     -+	/* TODO: Implement this using traverse_trees() */
     +-	/* TODO: Implement this using traverse_trees() */
       	die("Not yet implemented.");
       }
       
     @@ merge-ort.c: static void merge_ort_nonrecursive_internal(struct merge_options *o
       
      -	collect_merge_info(opt, merge_base, side1, side2);
      +	if (collect_merge_info(opt, merge_base, side1, side2) != 0) {
     ++		/*
     ++		 * TRANSLATORS: The %s arguments are: 1) tree hash of a merge
     ++		 * base, and 2-3) the trees for the two trees we're merging.
     ++		 */
      +		err(opt, _("collecting merge info failed for trees %s, %s, %s"),
      +		    oid_to_hex(&merge_base->object.oid),
      +		    oid_to_hex(&side1->object.oid),
  6:  ab743967aa !  6:  27268ef8a3 merge-ort: implement a very basic collect_merge_info()
     @@ merge-ort.c: static int err(struct merge_options *opt, const char *err, ...)
       			      struct tree *side1,
       			      struct tree *side2)
       {
     --	/* TODO: Implement this using traverse_trees() */
      -	die("Not yet implemented.");
      +	int ret;
      +	struct tree_desc t[3];
  7:  bff758c5dd =  7:  c6e5621c21 merge-ort: avoid repeating fill_tree_descriptor() on the same tree
  8:  61b3d66fdc =  8:  93fd69fa3c merge-ort: compute a few more useful fields for collect_merge_info
  9:  4e4298fa70 =  9:  decff4b375 merge-ort: record stage and auxiliary info for every path
 10:  3ec087eb68 = 10:  86c661fe1e merge-ort: avoid recursing into identical trees
 11:  0c89cee34e = 11:  aa3b13ffd8 merge-ort: add a preliminary simple process_entries() implementation
 12:  605cbc19d2 = 12:  b54306fd0e merge-ort: have process_entries operate in a defined order
 13:  242c3cab13 = 13:  8ee8561d7a merge-ort: step 1 of tree writing -- record basenames, modes, and oids
 14:  33a5d23c85 ! 14:  6ff56824c3 merge-ort: step 2 of tree writing -- function to create tree object
     @@ merge-ort.c: struct directory_versions {
       	struct string_list versions;
       };
       
     ++static int tree_entry_order(const void *a_, const void *b_)
     ++{
     ++	const struct string_list_item *a = a_;
     ++	const struct string_list_item *b = b_;
     ++
     ++	const struct merged_info *ami = a->util;
     ++	const struct merged_info *bmi = b->util;
     ++	return base_name_compare(a->string, strlen(a->string), ami->result.mode,
     ++				 b->string, strlen(b->string), bmi->result.mode);
     ++}
     ++
      +static void write_tree(struct object_id *result_oid,
      +		       struct string_list *versions,
      +		       unsigned int offset,
     @@ merge-ort.c: struct directory_versions {
      +	 */
      +	relevant_entries.items = versions->items + offset;
      +	relevant_entries.nr = versions->nr - offset;
     -+	string_list_sort(&relevant_entries);
     ++	QSORT(relevant_entries.items, relevant_entries.nr, tree_entry_order);
      +
      +	/* Pre-allocate some space in buf */
      +	extra = hash_size + 8; /* 8: 6 for mode, 1 for space, 1 for NUL char */
 15:  29615c366f ! 15:  da4fe90049 merge-ort: step 3 of tree writing -- handling subdirectories as we go
     @@ merge-ort.c: static int string_list_df_name_compare(const char *one, const char
      +	unsigned last_directory_len;
       };
       
     - static void write_tree(struct object_id *result_oid,
     + static int tree_entry_order(const void *a_, const void *b_)
      @@ merge-ort.c: static void record_entry_for_tree(struct directory_versions *dir_metadata,
       			   basename)->util = &mi->result;
       }
 16:  da54fa454a = 16:  8e90d211c5 merge-ort: basic outline for merge_switch_to_result()
 17:  68307f1b67 = 17:  61fada146c merge-ort: add implementation of checkout()
 18:  a3cd563621 = 18:  f5a13a0b08 tree: enable cmp_cache_name_compare() to be used elsewhere
 19:  56b162c609 ! 19:  4efac38116 merge-ort: add implementation of record_conflicted_index_entries()
     @@ merge-ort.c: static int record_conflicted_index_entries(struct merge_options *op
      +		pos = index_name_pos(index, path, strlen(path));
      +		SWAP(index->cache_nr, original_cache_nr);
      +		if (pos < 0) {
     -+			if (ci->filemask == 1)
     -+				cache_tree_invalidate_path(index, path);
     -+			else
     ++			if (ci->filemask != 1)
      +				BUG("Conflicted %s but nothing in basic working tree or index; this shouldn't happen", path);
     ++			cache_tree_invalidate_path(index, path);
      +		} else {
      +			ce = index->cache[pos];
      +
 20:  a4f722a46e = 20:  fbeb527d67 merge-ort: free data structures in merge_finalize()

-- 
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