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[PATCH v6 2/5] introduce submodule.superprojectGitDir record

From
Emily Shaffer <emilyshaffer@google.com>
Date
Nov 17, 2021, 00:56 UTC
Message-ID
<20211117005701.371808-3-emilyshaffer@google.com>
In-Reply-To
<20211117005701.371808-1-emilyshaffer@google.com>

Teach submodules a reference to their superproject's gitdir. This allows us to A) know that we're running from a submodule, and B) have a shortcut to the superproject's vitals, for example, configs.

By using a relative path instead of an absolute path, we can move the superproject directory around on the filesystem without breaking the submodule's pointer. And by using the path from gitdir to gitdir, we can move the submodule within the superproject's tree structure without breaking the submodule's pointer, too. Finally, by pointing at the superproject's worktree gitdir (if it exists), we ensure that we can tell which worktree contains our submodule.

Since this hint value is only introduced during new submodule creation via `git submodule add`, though, there is more work to do to allow the record to be created at other times.

Once this new config is reliably in place, we can use it to know definitively that we are working in a submodule, and to know which superproject we are a submodule of. This allows us to do some value-added behavior, like letting "git status" print additional info about the submodule's status in relation to its superproject, or like letting the superproject and submodule share an additional config file separate from either one's local config.

Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/config/submodule.txt | 12 +++++++++++
 builtin/submodule--helper.c        | 11 ++++++++++
 t/t7400-submodule-basic.sh         | 32 ++++++++++++++++++++----------
 3 files changed, 45 insertions(+), 10 deletions(-)
diff --git a/Documentation/config/submodule.txt b/Documentation/config/submodule.txt
index ee454f8126..61d975745e 100644
--- a/Documentation/config/submodule.txt
+++ b/Documentation/config/submodule.txt
@@ -91,3 +91,15 @@ 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 gitdir to its superproject's
+	gitdir. When Git is run in a repository, it usually makes no
+	difference whether this repository is standalone or a submodule, but if
+	this configuration variable is present, additional behavior may be
+	possible, such as "git status" printing additional information about
+	this submodule's status with respect to its superproject. This config
+	should only be present in projects which are submodules, but is not
+	guaranteed to be present in every submodule, so only optional
+	value-added behavior should be linked to it. It is set automatically
+	during submodule creation.
diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index e630f0c730..24f0ef2a78 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -1838,6 +1838,17 @@ static int clone_submodule(struct module_clone_data *clone_data)
 		git_config_set_in_file(p, "submodule.alternateErrorStrategy",
 				       error_strategy);
 
+	/*
+	 * Set the path from submodule's new gitdir to superproject's gitdir.
+	 * The latter may be a worktree gitdir. However, it is not possible for
+	 * the submodule to have a worktree-specific gitdir or config at clone
+	 * time, because "extensions.worktreeConfig" is only valid when set in
+	 * the local gitconfig, which the brand new submodule does not have yet.
+	 */
+	git_config_set_in_file(p, "submodule.superprojectGitDir",
+			       relative_path(absolute_path(get_git_dir()),
+					     sm_gitdir, &sb));
+
 	free(sm_alternate);
 	free(error_strategy);
 
diff --git a/t/t7400-submodule-basic.sh b/t/t7400-submodule-basic.sh
index d69a5c0032..3d146491df 100755
--- a/t/t7400-submodule-basic.sh
+++ b/t/t7400-submodule-basic.sh
@@ -109,12 +109,24 @@ submodurl=$(pwd -P)
 
 inspect() {
 	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 "$sub_dir" diff-files --exit-code &&
+
+	# Ensure that submodule.superprojectGitDir contains the path from the
+	# submodule's gitdir to the superproject's gitdir.
+
+	super_abs_gitdir=$(git -C "$super_dir" rev-parse --absolute-git-dir) &&
+	sub_abs_gitdir=$(git -C "$sub_dir" rev-parse --absolute-git-dir) &&
+
+	[ "$(git -C "$sub_dir" config --get submodule.superprojectGitDir)" = \
+	  "$(test-tool path-utils relative_path "$super_abs_gitdir" \
+						"$sub_abs_gitdir")" ] &&
+
 	git -C "$sub_dir" clean -n -d -x >untracked
 }
 
@@ -138,7 +150,7 @@ 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
@@ -240,7 +252,7 @@ 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
@@ -256,7 +268,7 @@ 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
@@ -272,7 +284,7 @@ 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
@@ -288,7 +300,7 @@ 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
@@ -304,7 +316,7 @@ 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
@@ -320,7 +332,7 @@ 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
@@ -351,7 +363,7 @@ 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
@@ -492,7 +504,7 @@ 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
 '
 
@@ -551,7 +563,7 @@ test_expect_success 'update should checkout rev1' '
 	echo "$rev1" >expect &&
 
 	git submodule update init &&
-	inspect init &&
+	inspect init . &&
 
 	test_cmp expect head-sha1
 '

-- 
2.34.0.rc1.387.gb447b232ab-goog
Previous: Emily ShafferNext: Jonathan Tan
Message 3 of 64 in “teach submodules to know they're submodules”
  1. 0/5 teach submodules to know they're submodulesEmily Shaffer, Nov 17, 2021
  2. 1/5 t7400-submodule-basic: modernize inspect() helperEmily Shaffer, Nov 17, 2021
  3. 2/5 introduce submodule.superprojectGitDir recordEmily Shaffer, Nov 17, 2021
  4. Jonathan TanNov 17, 2021
  5. 3/5 submodule: record superproject gitdir during absorbgitdirsEmily Shaffer, Nov 17, 2021
  6. 4/5 submodule: record superproject gitdir during 'update'Emily Shaffer, Nov 17, 2021
  7. 5/5 submodule: use config to find superproject worktreeEmily Shaffer, Nov 17, 2021
  8. 0/2 submodule: test what happens if submodule.superprojectGitDir isn't aroundÆvar Arnfjörð Bjarmason, Nov 17, 2021
  9. 1/2 submodule tests: fix potentially broken "config .. --unset"Ævar Arnfjörð Bjarmason, Nov 17, 2021
  10. 2/2 submodule: add test mode for checking absence of "superProjectGitDir"Ævar Arnfjörð Bjarmason, Nov 17, 2021
  11. Emily ShafferNov 23, 2021
  12. Ævar Arnfjörð BjarmasonNov 24, 2021
  13. Jonathan TanNov 17, 2021
  14. Emily ShafferNov 23, 2021
  15. 0/5 teach submodules to know they're submodulesEmily Shaffer, Feb 3, 2022
  16. 1/4 t7400-submodule-basic: modernize inspect() helperEmily Shaffer, Feb 3, 2022
  17. 2/4 introduce submodule.superprojectGitDir recordEmily Shaffer, Feb 3, 2022
  18. 3/4 submodule: record superproject gitdir during absorbgitdirsEmily Shaffer, Feb 3, 2022
  19. 4/4 submodule: record superproject gitdir during 'update'Emily Shaffer, Feb 3, 2022
  20. Junio C HamanoFeb 3, 2022
  21. Ævar Arnfjörð BjarmasonFeb 4, 2022
  22. Junio C HamanoFeb 4, 2022
  23. Jonathan NiederFeb 7, 2022
  24. Junio C HamanoFeb 7, 2022
  25. Jonathan NiederFeb 8, 2022
  26. Junio C HamanoFeb 8, 2022
  27. Emily ShafferFeb 10, 2022
  28. Jonathan NiederFeb 10, 2022
  29. Ævar Arnfjörð BjarmasonFeb 12, 2022
  30. Junio C HamanoFeb 13, 2022
  31. 0/3 teach submodules to know they're submodulesEmily Shaffer, Mar 1, 2022
  32. 1/3 t7400-submodule-basic: modernize inspect() helperEmily Shaffer, Mar 1, 2022
  33. 2/3 introduce submodule.hasSuperproject recordEmily Shaffer, Mar 1, 2022
  34. Junio C HamanoMar 1, 2022
  35. Emily ShafferMar 8, 2022
  36. Glen ChooMar 8, 2022
  37. Glen ChooMar 8, 2022
  38. 3/3 rev-parse: short-circuit superproject worktree when config unsetEmily Shaffer, Mar 1, 2022
  39. Junio C HamanoMar 1, 2022
  40. Emily ShafferMar 9, 2022
  41. Junio C HamanoMar 1, 2022
  42. Emily ShafferMar 8, 2022
  43. 0/3 teach submodules to know they're submodulesEmily Shaffer, Mar 10, 2022
  44. 1/3 t7400-submodule-basic: modernize inspect() helperEmily Shaffer, Mar 10, 2022
  45. 2/3 introduce submodule.hasSuperproject recordEmily Shaffer, Mar 10, 2022
  46. Junio C HamanoMar 10, 2022
  47. Glen ChooMar 10, 2022
  48. Glen ChooMar 10, 2022
  49. Junio C HamanoMar 10, 2022
  50. Glen ChooMar 10, 2022
  51. Glen ChooMar 10, 2022
  52. Emily ShafferMar 15, 2022
  53. Emily ShafferMar 15, 2022
  54. Glen ChooMar 15, 2022
  55. Emily ShafferMar 15, 2022
  56. Junio C HamanoMar 15, 2022
  57. Junio C HamanoMar 10, 2022
  58. Glen ChooMar 10, 2022
  59. Emily ShafferMar 15, 2022
  60. 3/3 rev-parse: short-circuit superproject worktree when config unsetEmily Shaffer, Mar 10, 2022
  61. Junio C HamanoMar 10, 2022
  62. Eric SunshineMar 10, 2022
  63. Ævar Arnfjörð BjarmasonMar 11, 2022
  64. Junio C HamanoMar 13, 2022

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