[PATCH v2 2/4] introduce submodule.superprojectGitDir cache

@@ -90,3 +90,15 @@ submodule.alternateErrorStrategy::
 	`ignore`, `info`, `die`. Default is `die`. Note that if set to `ignore`
 	or `info`, and if there is an error with the computed alternate, the
 	clone proceeds as if no alternate was specified.
+
+submodule.superprojectGitDir::
+	The relative path from the submodule's worktree  to the superproject's
+	gitdir. This config should only be present in projects which are
+	submodules, but is not guaranteed to be present in every submodule. It
+	is set automatically during submodule creation.
++
+	In situations where more than one superproject references the same
+	submodule worktree, the value of this config and the behavior of
+	operations which use it are undefined. To reference a single project
+	from multiple superprojects, it is better to create a worktree of the
+	submodule for each superproject.

@@ -1910,6 +1910,10 @@ static int module_clone(int argc, const char **argv, const char *prefix)
 		git_config_set_in_file(p, "submodule.alternateErrorStrategy",
 					   error_strategy);
 
+	git_config_set_in_file(p, "submodule.superprojectGitdir",
+			       relative_path(absolute_path(get_git_dir()),
+					     path, &sb));
+
 	free(sm_alternate);
 	free(error_strategy);
 

@@ -108,14 +108,18 @@ test_expect_success 'setup - repository to add submodules to' '
 submodurl=$(pwd -P)
 
 inspect() {
-	dir=$1 &&
-
-	git -C "$dir" for-each-ref --format='%(refname)' 'refs/heads/*' >heads &&
-	{ git -C "$dir" symbolic-ref HEAD || :; } >head &&
-	git -C "$dir" rev-parse HEAD >head-sha1 &&
-	git -C "$dir" update-index --refresh &&
-	git -C "$dir" diff-files --exit-code &&
-	git -C "$dir" clean -n -d -x >untracked
+	sub_dir=$1 &&
+	super_dir=$2 &&
+
+	git -C "$sub_dir" for-each-ref --format='%(refname)' 'refs/heads/*' >heads &&
+	{ git -C "$sub_dir" symbolic-ref HEAD || :; } >head &&
+	git -C "$sub_dir" rev-parse HEAD >head-sha1 &&
+	git -C "$sub_dir" update-index --refresh &&
+	git -C "$sub_dir" diff-files --exit-code &&
+	cached_super_dir="$(git -C "$sub_dir" config --get submodule.superprojectGitDir)" &&
+	[ "$(git -C "$super_dir" rev-parse --absolute-git-dir)" \
+		-ef "$sub_dir/$cached_super_dir" ] &&
+	git -C "$sub_dir" clean -n -d -x >untracked
 }
 
 

@@ -139,7 +143,7 @@ test_expect_success 'submodule add' '
 	) &&
 
 	rm -f heads head untracked &&
-	inspect addtest/submod &&
+	inspect addtest/submod addtest &&
 	test_cmp expect heads &&
 	test_cmp expect head &&
 	test_must_be_empty untracked

@@ -230,7 +234,7 @@ test_expect_success 'submodule add --branch' '
 	) &&
 
 	rm -f heads head untracked &&
-	inspect addtest/submod-branch &&
+	inspect addtest/submod-branch addtest &&
 	test_cmp expect-heads heads &&
 	test_cmp expect-head head &&
 	test_must_be_empty untracked

@@ -246,7 +250,7 @@ test_expect_success 'submodule add with ./ in path' '
 	) &&
 
 	rm -f heads head untracked &&
-	inspect addtest/dotsubmod/frotz &&
+	inspect addtest/dotsubmod/frotz addtest &&
 	test_cmp expect heads &&
 	test_cmp expect head &&
 	test_must_be_empty untracked

@@ -262,7 +266,7 @@ test_expect_success 'submodule add with /././ in path' '
 	) &&
 
 	rm -f heads head untracked &&
-	inspect addtest/dotslashdotsubmod/frotz &&
+	inspect addtest/dotslashdotsubmod/frotz addtest &&
 	test_cmp expect heads &&
 	test_cmp expect head &&
 	test_must_be_empty untracked

@@ -278,7 +282,7 @@ test_expect_success 'submodule add with // in path' '
 	) &&
 
 	rm -f heads head untracked &&
-	inspect addtest/slashslashsubmod/frotz &&
+	inspect addtest/slashslashsubmod/frotz addtest &&
 	test_cmp expect heads &&
 	test_cmp expect head &&
 	test_must_be_empty untracked

@@ -294,7 +298,7 @@ test_expect_success 'submodule add with /.. in path' '
 	) &&
 
 	rm -f heads head untracked &&
-	inspect addtest/realsubmod &&
+	inspect addtest/realsubmod addtest &&
 	test_cmp expect heads &&
 	test_cmp expect head &&
 	test_must_be_empty untracked

@@ -310,7 +314,7 @@ test_expect_success 'submodule add with ./, /.. and // in path' '
 	) &&
 
 	rm -f heads head untracked &&
-	inspect addtest/realsubmod2 &&
+	inspect addtest/realsubmod2 addtest &&
 	test_cmp expect heads &&
 	test_cmp expect head &&
 	test_must_be_empty untracked

@@ -341,7 +345,7 @@ test_expect_success 'submodule add in subdirectory' '
 	) &&
 
 	rm -f heads head untracked &&
-	inspect addtest/realsubmod3 &&
+	inspect addtest/realsubmod3 addtest &&
 	test_cmp expect heads &&
 	test_cmp expect head &&
 	test_must_be_empty untracked

@@ -482,7 +486,7 @@ test_expect_success 'update should work when path is an empty dir' '
 	git submodule update -q >update.out &&
 	test_must_be_empty update.out &&
 
-	inspect init &&
+	inspect init . &&
 	test_cmp expect head-sha1
 '
 

@@ -541,7 +545,7 @@ test_expect_success 'update should checkout rev1' '
 	echo "$rev1" >expect &&
 
 	git submodule update init &&
-	inspect init &&
+	inspect init . &&
 
 	test_cmp expect head-sha1
 '