[PATCH] merge-ort: turn submodule conflict suggestions into an advice

["Philippe Blain via GitGitGadget" <gitgitgadget@gmail.com>]

From: Philippe Blain <levraiphilippeblain@gmail.com>

Add a new advice type 'submoduleMergeConflict' for the error message
shown when a non-trivial submodule conflict is encountered, which was
added in 4057523a40 (submodule merge: update conflict error message,
2022-08-04). That commit mentions making this message an advice as
possible future work.

Update the tests as the expected message now appears on stderr instead
of stdout.

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
---
    merge-ort: turn submodule conflict suggestions into an advice

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1661%2Fphil-blain%2Fmerge-submodule-conflict-advice-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1661/phil-blain/merge-submodule-conflict-advice-v1
Pull-Request: https://github.com/git/git/pull/1661

 Documentation/config/advice.txt |  3 +++
 advice.c                        |  1 +
 advice.h                        |  1 +
 merge-ort.c                     |  3 ++-
 t/t6437-submodule-merge.sh      | 14 +++++++-------
 t/t7402-submodule-rebase.sh     |  2 +-
 6 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index 25c09175244..32701b96828 100644
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -128,6 +128,9 @@ advice.*::
 	submoduleAlternateErrorStrategyDie::
 		Advice shown when a submodule.alternateErrorStrategy option
 		configured to "die" causes a fatal error.
+	submoduleMergeConflict::
+		Advice shown when a non-trivial submodule merge conflict is
+		encountered.
 	submodulesNotUpdated::
 		Advice shown when a user runs a submodule command that fails
 		because `git submodule update --init` was not run.
diff --git a/advice.c b/advice.c
index f6e4c2f302e..eee27b5bebc 100644
--- a/advice.c
+++ b/advice.c
@@ -73,6 +73,7 @@ static struct {
 	[ADVICE_STATUS_U_OPTION]			= { "statusUoption", 1 },
 	[ADVICE_SUBMODULES_NOT_UPDATED] 		= { "submodulesNotUpdated", 1 },
 	[ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE] = { "submoduleAlternateErrorStrategyDie", 1 },
+	[ADVICE_SUBMODULE_MERGE_CONFLICT]               = { "submoduleMergeConflict", 1  },
 	[ADVICE_SUGGEST_DETACHING_HEAD]			= { "suggestDetachingHead", 1 },
 	[ADVICE_UPDATE_SPARSE_PATH]			= { "updateSparsePath", 1 },
 	[ADVICE_WAITING_FOR_EDITOR]			= { "waitingForEditor", 1 },
diff --git a/advice.h b/advice.h
index 9d4f49ae38b..7d0a821f5cb 100644
--- a/advice.h
+++ b/advice.h
@@ -47,6 +47,7 @@ enum advice_type {
 	ADVICE_STATUS_U_OPTION,
 	ADVICE_SUBMODULES_NOT_UPDATED,
 	ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE,
+	ADVICE_SUBMODULE_MERGE_CONFLICT,
 	ADVICE_SUGGEST_DETACHING_HEAD,
 	ADVICE_UPDATE_SPARSE_PATH,
 	ADVICE_WAITING_FOR_EDITOR,
diff --git a/merge-ort.c b/merge-ort.c
index 77ba7f3020c..59f025db26f 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -18,6 +18,7 @@
 #include "merge-ort.h"
 
 #include "alloc.h"
+#include "advice.h"
 #include "attr.h"
 #include "cache-tree.h"
 #include "commit.h"
@@ -4555,7 +4556,7 @@ static void print_submodule_conflict_suggestion(struct string_list *csub) {
 		      " - commit the resulting index in the superproject\n"),
 		    tmp.buf, subs.buf);
 
-	printf("%s", msg.buf);
+	advise_if_enabled(ADVICE_SUBMODULE_MERGE_CONFLICT, "%s", msg.buf);
 
 	strbuf_release(&subs);
 	strbuf_release(&tmp);
diff --git a/t/t6437-submodule-merge.sh b/t/t6437-submodule-merge.sh
index 70650521b04..7a3f1cb27c1 100755
--- a/t/t6437-submodule-merge.sh
+++ b/t/t6437-submodule-merge.sh
@@ -113,7 +113,7 @@ test_expect_success 'merging should conflict for non fast-forward' '
 	 git checkout -b test-nonforward-a b &&
 	  if test "$GIT_TEST_MERGE_ALGORITHM" = ort
 	  then
-		test_must_fail git merge c >actual &&
+		test_must_fail git merge c 2>actual &&
 		sub_expect="go to submodule (sub), and either merge commit $(git -C sub rev-parse --short sub-c)" &&
 		grep "$sub_expect" actual
 	  else
@@ -154,9 +154,9 @@ test_expect_success 'merging should conflict for non fast-forward (resolution ex
 	  git rev-parse --short sub-d > ../expect) &&
 	  if test "$GIT_TEST_MERGE_ALGORITHM" = ort
 	  then
-		test_must_fail git merge c >actual &&
+		test_must_fail git merge c >actual 2>sub-actual &&
 		sub_expect="go to submodule (sub), and either merge commit $(git -C sub rev-parse --short sub-c)" &&
-		grep "$sub_expect" actual
+		grep "$sub_expect" sub-actual
 	  else
 		test_must_fail git merge c 2> actual
 	  fi &&
@@ -181,9 +181,9 @@ test_expect_success 'merging should fail for ambiguous common parent' '
 	 ) &&
 	 if test "$GIT_TEST_MERGE_ALGORITHM" = ort
 	 then
-		test_must_fail git merge c >actual &&
+		test_must_fail git merge c >actual 2>sub-actual &&
 		sub_expect="go to submodule (sub), and either merge commit $(git -C sub rev-parse --short sub-c)" &&
-		grep "$sub_expect" actual
+		grep "$sub_expect" sub-actual
 	 else
 		test_must_fail git merge c 2> actual
 	 fi &&
@@ -227,7 +227,7 @@ test_expect_success 'merging should fail for changes that are backwards' '
 	git commit -a -m "f" &&
 
 	git checkout -b test-backward e &&
-	test_must_fail git merge f >actual &&
+	test_must_fail git merge f 2>actual &&
 	if test "$GIT_TEST_MERGE_ALGORITHM" = ort
     then
 		sub_expect="go to submodule (sub), and either merge commit $(git -C sub rev-parse --short sub-d)" &&
@@ -535,7 +535,7 @@ test_expect_success 'merging should fail with no merge base' '
 	git checkout -b b init &&
 	git add sub &&
 	git commit -m "b" &&
-	test_must_fail git merge a >actual &&
+	test_must_fail git merge a 2>actual &&
 	if test "$GIT_TEST_MERGE_ALGORITHM" = ort
     then
 		sub_expect="go to submodule (sub), and either merge commit $(git -C sub rev-parse --short HEAD^1)" &&
diff --git a/t/t7402-submodule-rebase.sh b/t/t7402-submodule-rebase.sh
index 2b3c363078b..aa2fdc31d1a 100755
--- a/t/t7402-submodule-rebase.sh
+++ b/t/t7402-submodule-rebase.sh
@@ -116,7 +116,7 @@ test_expect_success 'rebasing submodule that should conflict' '
 	test_tick &&
 	git commit -m fourth &&
 
-	test_must_fail git rebase --onto HEAD^^ HEAD^ HEAD^0 >actual_output &&
+	test_must_fail git rebase --onto HEAD^^ HEAD^ HEAD^0 2>actual_output &&
 	git ls-files -s submodule >actual &&
 	(
 		cd submodule &&

base-commit: b50a608ba20348cb3dfc16a696816d51780e3f0f
-- 
gitgitgadget