Merge branch 'mp/absorb-submodule-git-dir-upon-deinit'

"git submodule deinit" for a submodule whose .git metadata
directory is embedded in its working tree refused to work, until
the submodule gets converted to use the "absorbed" form where the
metadata directory is stored in superproject, and a gitfile at the
top-level of the working tree of the submodule points at it.  The
command is taught to convert such submodules to the absorbed form
as needed.

* mp/absorb-submodule-git-dir-upon-deinit:
  submodule: absorb git dir instead of dying on deinit

builtin/submodule--helper.c

@@ -1503,16 +1503,17 @@ static void deinit_submodule(const char *path, const char *prefix,
 		struct strbuf sb_rm = STRBUF_INIT;
 		const char *format;
 
-		/*
-		 * protect submodules containing a .git directory
-		 * NEEDSWORK: instead of dying, automatically call
-		 * absorbgitdirs and (possibly) warn.
-		 */
-		if (is_directory(sub_git_dir))
-			die(_("Submodule work tree '%s' contains a .git "
-			      "directory (use 'rm -rf' if you really want "
-			      "to remove it including all of its history)"),
-			    displaypath);
+		if (is_directory(sub_git_dir)) {
+			if (!(flags & OPT_QUIET))
+				warning(_("Submodule work tree '%s' contains a .git "
+					  "directory. This will be replaced with a "
+					  ".git file by using absorbgitdirs."),
+					displaypath);
+
+			absorb_git_dir_into_superproject(path,
+							 ABSORB_GITDIR_RECURSE_SUBMODULES);
+
+		}
 
 		if (!(flags & OPT_FORCE)) {
 			struct child_process cp_rm = CHILD_PROCESS_INIT;

t/t7400-submodule-basic.sh

@@ -1182,18 +1182,17 @@ test_expect_success 'submodule deinit is silent when used on an uninitialized su
 	rmdir init example2
 '
 
-test_expect_success 'submodule deinit fails when submodule has a .git directory even when forced' '
+test_expect_success 'submodule deinit absorbs .git directory if .git is a directory' '
 	git submodule update --init &&
 	(
 		cd init &&
 		rm .git &&
-		cp -R ../.git/modules/example .git &&
+		mv ../.git/modules/example .git &&
 		GIT_WORK_TREE=. git config --unset core.worktree
 	) &&
-	test_must_fail git submodule deinit init &&
-	test_must_fail git submodule deinit -f init &&
-	test -d init/.git &&
-	test -n "$(git config --get-regexp "submodule\.example\.")"
+	git submodule deinit init &&
+	test_path_is_missing init/.git &&
+	test -z "$(git config --get-regexp "submodule\.example\.")"
 '
 
 test_expect_success 'submodule with UTF-8 name' '