[PATCH v6 4/4] branch: let --delete-integrated find branches merged onto changed files

@@ -240,11 +240,14 @@ remove it anyway.
 	Like `--delete-merged`, but also delete a branch whose changes
 	the upstream already has even though its commits are not there,
 	as happens after a squash or rebase merge. Such a branch is
-	deleted when some upstream commit since the fork point has its
-	version of every file it changed, even if those changes were
-	later reverted, and the message names the first such commit.
-	It does not matter who made that commit. The same rules for
-	which branches are kept apply as for `--delete-merged`.
+	deleted when some upstream commit since the fork point has all
+	of its changes, even if they were later reverted, and the
+	message names the first such commit. It does not matter who made
+	that commit. A file counts when the commit has the branch's
+	version of it, or when merging the branch's version into the
+	commit's leaves it unchanged, which reads the file and may
+	download blobs in a partial clone. The same rules for which
+	branches are kept apply as for `--delete-merged`.
 
 `--dry-run`::
 	With `--delete-merged` or `--delete-integrated`, print which

@@ -33,8 +33,10 @@
 #include "diff.h"
 #include "diffcore.h"
 #include "hex.h"
+#include "merge-ll.h"
 #include "revision.h"
 #include "tree-walk.h"
+#include "xdiff-interface.h"
 
 static const char * const builtin_branch_usage[] = {
 	N_("git branch [<options>] [-r | -a] [--merged] [--no-merged] [(--forked <branch>)...]"),

@@ -853,10 +855,17 @@ static int branch_pushes_to_upstream(struct branch *branch,
 	return ret;
 }
 
+enum change_state {
+	CHANGE_MISSING,
+	CHANGE_LANDED,
+	CHANGE_NEEDS_MERGE,
+};
+
 struct branch_change {
 	char *path;
-	struct object_id branch_oid;
+	struct object_id base_oid, branch_oid, upstream_oid;
 	unsigned short branch_mode;
+	enum change_state state;
 };
 
 struct landing_search {

@@ -888,6 +897,8 @@ static void collect_branch_changes(struct landing_search *search,
 			   search->changes_alloc);
 		change = &search->changes[search->changes_nr++];
 		change->path = xstrdup(p->two->path);
+		oidcpy(&change->base_oid, DIFF_FILE_VALID(p->one) ?
+		       &p->one->oid : null_oid(the_hash_algo));
 		oidcpy(&change->branch_oid, DIFF_FILE_VALID(p->two) ?
 		       &p->two->oid : null_oid(the_hash_algo));
 		change->branch_mode = p->two->mode;

@@ -895,25 +906,66 @@ static void collect_branch_changes(struct landing_search *search,
 	diff_flush(&diffopt);
 }
 
-static int change_landed(const struct branch_change *change,
-			 struct commit *commit)
+static int merge_keeps_upstream(const struct branch_change *change)
+{
+	mmfile_t base, upstream, branch;
+	mmfile_t result = { 0 };
+	int ret;
+
+	repo_read_index(the_repository);
+	read_mmblob(&base, the_repository->objects, &change->base_oid);
+	read_mmblob(&upstream, the_repository->objects, &change->upstream_oid);
+	read_mmblob(&branch, the_repository->objects, &change->branch_oid);
+	ret = ll_merge(&result, change->path, &base, "base",
+		       &upstream, "upstream", &branch, "branch",
+		       the_repository->index, NULL) == LL_MERGE_OK &&
+	      result.size == upstream.size &&
+	      !memcmp(result.ptr, upstream.ptr, upstream.size);
+
+	free(base.ptr);
+	free(upstream.ptr);
+	free(branch.ptr);
+	free(result.ptr);
+	return ret;
+}
+
+static enum change_state change_state_at(struct branch_change *change,
+					 struct commit *commit)
 {
-	struct object_id oid;
 	unsigned short mode;
 
 	if (get_tree_entry(the_repository, get_commit_tree_oid(commit),
-			   change->path, &oid, &mode))
-		return is_null_oid(&change->branch_oid);
-	return oideq(&oid, &change->branch_oid) &&
-	       mode == change->branch_mode;
+			   change->path, &change->upstream_oid, &mode))
+		return is_null_oid(&change->branch_oid) ?
+			CHANGE_LANDED : CHANGE_MISSING;
+	if (oideq(&change->upstream_oid, &change->branch_oid))
+		return mode == change->branch_mode ?
+			CHANGE_LANDED : CHANGE_MISSING;
+	if (is_null_oid(&change->base_oid) ||
+	    is_null_oid(&change->branch_oid) ||
+	    oideq(&change->upstream_oid, &change->base_oid) ||
+	    mode != change->branch_mode || !S_ISREG(mode))
+		return CHANGE_MISSING;
+	return CHANGE_NEEDS_MERGE;
 }
 
 static int changes_landed(struct landing_search *search,
 			  struct commit *commit)
 {
-	for (size_t i = 0; i < search->changes_nr; i++)
-		if (!change_landed(&search->changes[i], commit))
+	for (size_t i = 0; i < search->changes_nr; i++) {
+		struct branch_change *change = &search->changes[i];
+
+		change->state = change_state_at(change, commit);
+		if (change->state == CHANGE_MISSING)
 			return 0;
+	}
+	for (size_t i = 0; i < search->changes_nr; i++) {
+		struct branch_change *change = &search->changes[i];
+
+		if (change->state == CHANGE_NEEDS_MERGE &&
+		    !merge_keeps_upstream(change))
+			return 0;
+	}
 	return 1;
 }
 

@@ -2122,6 +2122,48 @@ test_expect_success '--delete-integrated deletes a squash merged branch that was
 	)
 '
 
+test_expect_success '--delete-integrated deletes a squash merged branch after upstream changed the same file' '
+	(
+		cd upstream &&
+		git checkout next &&
+		test_write_lines 1 2 3 4 5 6 7 8 9 10 >shared &&
+		git add shared &&
+		git commit -m "add shared" &&
+		git checkout main
+	) &&
+	setup_repo_for_delete_merged &&
+	(
+		cd repo &&
+		git checkout -b edits-shared --track origin/next &&
+		test_write_lines 1 two 3 4 5 6 7 8 9 10 >shared &&
+		git commit -a -m "edit line 2" &&
+		git push origin edits-shared &&
+		git checkout --detach
+	) &&
+	(
+		cd upstream &&
+		git checkout next &&
+		test_write_lines 1 2 3 4 five 6 7 8 9 10 >shared &&
+		git commit -a -m "edit line 5" &&
+		git checkout main
+	) &&
+	squash_merge_upstream edits-shared &&
+	squash=$(git -C upstream rev-parse --short next) &&
+	(
+		cd repo &&
+		git fetch origin &&
+		sha=$(git rev-parse --short edits-shared) &&
+
+		git branch --delete-integrated origin/next >actual 2>&1 &&
+		echo "Deleted branch edits-shared (was $sha, landed as $squash)." >expect &&
+		test_cmp expect actual &&
+
+		check_branches <<-\EOF
+		main
+		EOF
+	)
+'
+
 test_expect_success '--delete-integrated reports a merge plainly next to an unmerged branch' '
 	setup_repo_for_delete_merged &&
 	push_topic a-unmerged unmerged-work &&