1 files changed, 35 insertions, 7 deletions

diff --git a/submodule.c b/submodule.c
index a2701ede4a..d393e947e6 100644
--- a/submodule.c
+++ b/submodule.c
@@ -52,6 +52,24 @@ int is_gitmodules_unmerged(const struct index_state *istate)
 }
 
 /*
+ * Check if the .gitmodules file is safe to write.
+ *
+ * Writing to the .gitmodules file requires that the file exists in the
+ * working tree or, if it doesn't, that a brand new .gitmodules file is going
+ * to be created (i.e. it's neither in the index nor in the current branch).
+ *
+ * It is not safe to write to .gitmodules if it's not in the working tree but
+ * it is in the index or in the current branch, because writing new values
+ * (and staging them) would blindly overwrite ALL the old content.
+ */
+int is_writing_gitmodules_ok(void)
+{
+	struct object_id oid;
+	return file_exists(GITMODULES_FILE) ||
+		(get_oid(GITMODULES_INDEX, &oid) < 0 && get_oid(GITMODULES_HEAD, &oid) < 0);
+}
+
+/*
  * Check if the .gitmodules file has unstaged modifications.  This must be
  * checked before allowing modifications to the .gitmodules file with the
  * intention to stage them later, because when continuing we would stage the
@@ -89,6 +107,7 @@ int update_path_in_gitmodules(const char *oldpath, const char *newpath)
 {
 	struct strbuf entry = STRBUF_INIT;
 	const struct submodule *submodule;
+	int ret;
 
 	if (!file_exists(GITMODULES_FILE)) /* Do nothing without .gitmodules */
 		return -1;
@@ -104,14 +123,9 @@ int update_path_in_gitmodules(const char *oldpath, const char *newpath)
 	strbuf_addstr(&entry, "submodule.");
 	strbuf_addstr(&entry, submodule->name);
 	strbuf_addstr(&entry, ".path");
-	if (git_config_set_in_file_gently(GITMODULES_FILE, entry.buf, newpath) < 0) {
-		/* Maybe the user already did that, don't error out here */
-		warning(_("Could not update .gitmodules entry %s"), entry.buf);
-		strbuf_release(&entry);
-		return -1;
-	}
+	ret = config_set_in_gitmodules_file_gently(entry.buf, newpath);
 	strbuf_release(&entry);
-	return 0;
+	return ret;
 }
 
 /*
@@ -1547,6 +1561,18 @@ out:
 	return ret;
 }
 
+void submodule_unset_core_worktree(const struct submodule *sub)
+{
+	char *config_path = xstrfmt("%s/modules/%s/config",
+				    get_git_common_dir(), sub->name);
+
+	if (git_config_set_in_file_gently(config_path, "core.worktree", NULL))
+		warning(_("Could not unset core.worktree setting in submodule '%s'"),
+			  sub->path);
+
+	free(config_path);
+}
+
 static const char *get_super_prefix_or_empty(void)
 {
 	const char *s = get_super_prefix();
@@ -1712,6 +1738,8 @@ int submodule_move_head(const char *path,
 
 			if (is_empty_dir(path))
 				rmdir_or_warn(path);
+
+			submodule_unset_core_worktree(sub);
 		}
 	}
 out: