submodule: fetch missing objects from default remote

When be76c21282 (fetch: ensure submodule objects fetched, 2018-12-06)
added support for fetching a missing submodule object by id, it
hardcoded the remote name as "origin" and deferred anything more
complicated for a later patch. Implement the NEEDSWORK item to remove
the hardcoded assumption by adding and using a submodule helper subcmd
'get-default-remote'. Fixing this lets 'git fetch --recurse-submodules'
succeed when the fetched commit(s) in the superproject trigger a
submodule fetch, and that submodule's default remote name is not
"origin".

Add non-"origin" remote tests to t5526-fetch-submodules.sh and
t5572-pull-submodule.sh demonstrating this works as expected and add
dedicated tests for get-default-remote.

Signed-off-by: Nasser Grainawi <nasser.grainawi@oss.qualcomm.com>
Reviewed-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 277 insertions, 2 deletions

diff --git a/t/meson.build b/t/meson.build
index 459c52a489..6ff54cf276 100644
--- a/t/meson.build
+++ b/t/meson.build
@@ -887,6 +887,7 @@ integration_tests = [
   't7422-submodule-output.sh',
   't7423-submodule-symlinks.sh',
   't7424-submodule-mixed-ref-formats.sh',
+  't7426-submodule-get-default-remote.sh',
   't7450-bad-git-dotfiles.sh',
   't7500-commit-template-squash-signoff.sh',
   't7501-commit-basic-functionality.sh',
diff --git a/t/t5526-fetch-submodules.sh b/t/t5526-fetch-submodules.sh
index 5e566205ba..1242ee9185 100755
--- a/t/t5526-fetch-submodules.sh
+++ b/t/t5526-fetch-submodules.sh
@@ -834,11 +834,18 @@ test_expect_success "fetch new submodule commits on-demand outside standard refs
 	git commit -m "updated submodules outside of refs/heads" &&
 	E=$(git rev-parse HEAD) &&
 	git update-ref refs/changes/3 $E &&
+	FETCH_TRACE="$(pwd)/trace.out" &&
+	test_when_finished "rm -f \"$FETCH_TRACE\"" &&
 	(
 		cd downstream &&
-		git fetch --recurse-submodules origin refs/changes/3:refs/heads/my_branch &&
+		GIT_TRACE="$FETCH_TRACE" git fetch --recurse-submodules origin \
+			refs/changes/3:refs/heads/my_branch &&
 		git -C submodule cat-file -t $C &&
 		git -C sub1 cat-file -t $D &&
+		test_grep "trace: built-in: git submodule--helper get-default-remote sub1" \
+			"$FETCH_TRACE" &&
+		test_grep "trace: built-in: git fetch .* --submodule-prefix=sub1/ origin" \
+			"$FETCH_TRACE" &&
 		git checkout --recurse-submodules FETCH_HEAD
 	)
 '
@@ -929,6 +936,68 @@ test_expect_success 'fetch new submodule commit intermittently referenced by sup
 	)
 '
 
+test_expect_success 'fetch new submodule commits on-demand outside standard refspec with custom remote name' '
+	# depends on the previous test for setup
+
+	# Rename the remote in sub1 from "origin" to "custom_remote"
+	git -C downstream/sub1 remote rename origin custom_remote &&
+
+	# Create new commits in the original submodules
+	C=$(git -C submodule commit-tree \
+		-m "change outside refs/heads for custom remote" HEAD^{tree}) &&
+	git -C submodule update-ref refs/changes/custom1 $C &&
+	git update-index --cacheinfo 160000 $C submodule &&
+	test_tick &&
+
+	D=$(git -C sub1 commit-tree \
+		-m "change outside refs/heads for custom remote" HEAD^{tree}) &&
+	git -C sub1 update-ref refs/changes/custom2 $D &&
+	git update-index --cacheinfo 160000 $D sub1 &&
+
+	git commit \
+		-m "updated submodules outside of refs/heads for custom remote" &&
+	E=$(git rev-parse HEAD) &&
+	git update-ref refs/changes/custom3 $E &&
+	FETCH_TRACE="$(pwd)/trace.out" &&
+	test_when_finished "rm -f \"$FETCH_TRACE\"" &&
+	(
+		cd downstream &&
+		GIT_TRACE="$FETCH_TRACE" git fetch --recurse-submodules origin \
+			refs/changes/custom3:refs/heads/my_other_branch &&
+		git -C submodule cat-file -t $C &&
+		git -C sub1 cat-file -t $D &&
+		test_grep "trace: built-in: git submodule--helper get-default-remote sub1" \
+			"$FETCH_TRACE" &&
+		test_grep "trace: built-in: git fetch .* --submodule-prefix=sub1/ custom_remote $D" \
+			"$FETCH_TRACE" &&
+		git checkout --recurse-submodules FETCH_HEAD
+	)
+'
+
+test_expect_success 'fetch new submodule commit on-demand in FETCH_HEAD from custom remote' '
+	# depends on the previous test for setup
+
+	C=$(git -C submodule commit-tree -m "another change outside refs/heads for custom remote" HEAD^{tree}) &&
+	git -C submodule update-ref refs/changes/custom4 $C &&
+	git update-index --cacheinfo 160000 $C submodule &&
+	test_tick &&
+
+	D=$(git -C sub1 commit-tree -m "another change outside refs/heads for custom remote" HEAD^{tree}) &&
+	git -C sub1 update-ref refs/changes/custom5 $D &&
+	git update-index --cacheinfo 160000 $D sub1 &&
+
+	git commit -m "updated submodules outside of refs/heads" &&
+	E=$(git rev-parse HEAD) &&
+	git update-ref refs/changes/custom6 $E &&
+	(
+		cd downstream &&
+		git fetch --recurse-submodules origin refs/changes/custom6 &&
+		git -C submodule cat-file -t $C &&
+		git -C sub1 cat-file -t $D &&
+		git checkout --recurse-submodules FETCH_HEAD
+	)
+'
+
 add_commit_push () {
 	dir="$1" &&
 	msg="$2" &&
diff --git a/t/t5572-pull-submodule.sh b/t/t5572-pull-submodule.sh
index 45f384dd32..42d14328b6 100755
--- a/t/t5572-pull-submodule.sh
+++ b/t/t5572-pull-submodule.sh
@@ -257,7 +257,26 @@ test_expect_success 'fetch submodule remote of different name from superproject'
 	git -C a-submodule reset --hard HEAD^^ &&
 
 	git -C child pull --no-recurse-submodules &&
-	git -C child submodule update
+	git -C child submodule update &&
+	test_path_is_file child/a-submodule/moreecho.t
+'
+
+test_expect_success 'fetch non-origin submodule remote named different from superproject' '
+	git -C child/a-submodule remote rename origin o2 &&
+
+	# Create commit that is unreachable from current master branch
+	# newmain is already reset in the previous test
+	test_commit -C a-submodule echo_o2 &&
+	test_commit -C a-submodule moreecho_o2 &&
+	subc=$(git -C a-submodule rev-parse --short HEAD) &&
+
+	git -C parent/a-submodule fetch &&
+	git -C parent/a-submodule checkout "$subc" &&
+	git -C parent commit -m "update submodule o2" a-submodule &&
+	git -C a-submodule reset --hard HEAD^^ &&
+
+	git -C child pull --recurse-submodules &&
+	test_path_is_file child/a-submodule/moreecho_o2.t
 '
 
 test_done
diff --git a/t/t7426-submodule-get-default-remote.sh b/t/t7426-submodule-get-default-remote.sh
new file mode 100755
index 0000000000..b842af9a2d
--- /dev/null
+++ b/t/t7426-submodule-get-default-remote.sh
@@ -0,0 +1,186 @@
+#!/bin/sh
+
+test_description='git submodule--helper get-default-remote'
+
+TEST_NO_CREATE_REPO=1
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	git config --global protocol.file.allow always
+'
+
+test_expect_success 'setup repositories' '
+	# Create a repository to be used as submodule
+	git init sub &&
+	test_commit --no-tag -C sub "initial commit in sub" file.txt "sub content" &&
+
+	# Create main repository
+	git init super &&
+	(
+		cd super &&
+		mkdir subdir &&
+		test_commit --no-tag -C subdir "initial commit in super" main.txt "super content" &&
+		git submodule add ../sub subpath &&
+		git commit -m "add submodule 'sub' at subpath"
+	)
+'
+
+test_expect_success 'get-default-remote returns origin for initialized submodule' '
+	(
+		cd super &&
+		git submodule update --init &&
+		echo "origin" >expect &&
+		git submodule--helper get-default-remote subpath >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'get-default-remote works from subdirectory' '
+	(
+		cd super/subdir &&
+		echo "origin" >expect &&
+		git submodule--helper get-default-remote ../subpath >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'get-default-remote fails with non-existent path' '
+	(
+		cd super &&
+		test_must_fail git submodule--helper get-default-remote nonexistent 2>err &&
+		test_grep "could not get a repository handle" err
+	)
+'
+
+test_expect_success 'get-default-remote fails with non-submodule path' '
+	(
+		cd super &&
+		test_must_fail git submodule--helper get-default-remote subdir 2>err &&
+		test_grep "could not get a repository handle" err
+	)
+'
+
+test_expect_success 'get-default-remote fails without path argument' '
+	(
+		cd super &&
+		test_must_fail git submodule--helper get-default-remote 2>err &&
+		test_grep "usage:" err
+	)
+'
+
+test_expect_success 'get-default-remote fails with too many arguments' '
+	(
+		cd super &&
+		test_must_fail git submodule--helper get-default-remote subpath subdir 2>err &&
+		test_grep "usage:" err
+	)
+'
+
+test_expect_success 'setup submodule with non-origin default remote name' '
+	# Create another submodule path with a different remote name
+	(
+		cd super &&
+		git submodule add ../sub upstream-subpath &&
+		git commit -m "add second submodule in upstream-subpath" &&
+		git submodule update --init upstream-subpath &&
+
+		# Change the remote name in the submodule
+		cd upstream-subpath &&
+		git remote rename origin upstream
+	)
+'
+
+test_expect_success 'get-default-remote returns non-origin remote name' '
+	(
+		cd super &&
+		echo "upstream" >expect &&
+		git submodule--helper get-default-remote upstream-subpath >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'get-default-remote handles submodule with multiple remotes' '
+	(
+		cd super/subpath &&
+		git remote add other-upstream ../../sub &&
+		git remote add myfork ../../sub
+	) &&
+
+	(
+		cd super &&
+		echo "origin" >expect &&
+		git submodule--helper get-default-remote subpath >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'get-default-remote handles submodule with multiple remotes and none are origin' '
+	(
+		cd super/upstream-subpath &&
+		git remote add yet-another-upstream ../../sub &&
+		git remote add yourfork ../../sub
+	) &&
+
+	(
+		cd super &&
+		echo "upstream" >expect &&
+		git submodule--helper get-default-remote upstream-subpath >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'setup nested submodule with non-origin remote' '
+	git init innersub &&
+	test_commit --no-tag -C innersub "initial commit in innersub" inner.txt "innersub content" &&
+
+	(
+		cd sub &&
+		git submodule add ../innersub innersubpath &&
+		git commit -m "add nested submodule at innersubpath"
+	) &&
+
+	(
+		cd super/upstream-subpath &&
+		git pull upstream &&
+		git submodule update --init --recursive . &&
+		(
+			cd innersubpath &&
+			git remote rename origin another_upstream
+		)
+	)
+'
+
+test_expect_success 'get-default-remote works with nested submodule' '
+	(
+		cd super &&
+		echo "another_upstream" >expect &&
+		git submodule--helper get-default-remote upstream-subpath/innersubpath >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'get-default-remote works with submodule that has no remotes' '
+	# Create a submodule directory manually without remotes
+	(
+		cd super &&
+		git init no-remote-sub &&
+		test_commit --no-tag -C no-remote-sub "local commit" local.txt "local content"
+	) &&
+
+	# Add it as a submodule
+	(
+		cd super &&
+		git submodule add ./no-remote-sub &&
+		git commit -m "add local submodule 'no-remote-sub'"
+	) &&
+
+	(
+		cd super &&
+		# Should fall back to "origin" remote name when no remotes exist
+		echo "origin" >expect &&
+		git submodule--helper get-default-remote no-remote-sub >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_done