[PATCH v2 02/12] worktree: skip reading HEAD when repairing worktrees

[Patrick Steinhardt <ps@pks.im>]

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When calling `git init --separate-git-dir=<new-path>` on a preexisting
repository, we move the Git directory of that repository to the new path
specified by the user. If there are worktrees present in the repository,
we need to repair the worktrees so that their gitlinks point to the new
location of the repository.

This repair logic will load repositories via `get_worktrees()`, which
will enumerate up and initialize all worktrees. Part of initialization
is logic that we resolve their respective worktree HEADs, even though
that information may not actually be needed in the end by all callers.

In the context of git-init(1) this is about to become a problem, because
we do not have a repository that was set up via `setup_git_directory()`
or friends. Consequentially, it is not yet fully initialized at the time
of calling `repair_worktrees()`, and properly setting up all parts of
the repository in `init_db()` before we repair worktrees is not an easy
thing to do. While this is okay right now where we only have a single
reference backend in Git, once we gain a second one we would be trying
to look up the worktree HEADs before we have figured out the reference
format, which does not work.

We do not require the worktree HEADs at all to repair worktrees. So
let's fix this issue by skipping over the step that reads them.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 worktree.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/worktree.c b/worktree.c
index a56a6c2a3d..9702ed0308 100644
--- a/worktree.c
+++ b/worktree.c
@@ -51,7 +51,7 @@ static void add_head_info(struct worktree *wt)
 /**
  * get the main worktree
  */
-static struct worktree *get_main_worktree(void)
+static struct worktree *get_main_worktree(int skip_reading_head)
 {
 	struct worktree *worktree = NULL;
 	struct strbuf worktree_path = STRBUF_INIT;
@@ -70,11 +70,13 @@ static struct worktree *get_main_worktree(void)
 	 */
 	worktree->is_bare = (is_bare_repository_cfg == 1) ||
 		is_bare_repository();
-	add_head_info(worktree);
+	if (!skip_reading_head)
+		add_head_info(worktree);
 	return worktree;
 }
 
-static struct worktree *get_linked_worktree(const char *id)
+static struct worktree *get_linked_worktree(const char *id,
+					    int skip_reading_head)
 {
 	struct worktree *worktree = NULL;
 	struct strbuf path = STRBUF_INIT;
@@ -93,7 +95,8 @@ static struct worktree *get_linked_worktree(const char *id)
 	CALLOC_ARRAY(worktree, 1);
 	worktree->path = strbuf_detach(&worktree_path, NULL);
 	worktree->id = xstrdup(id);
-	add_head_info(worktree);
+	if (!skip_reading_head)
+		add_head_info(worktree);
 
 done:
 	strbuf_release(&path);
@@ -118,7 +121,7 @@ static void mark_current_worktree(struct worktree **worktrees)
 	free(git_dir);
 }
 
-struct worktree **get_worktrees(void)
+static struct worktree **get_worktrees_internal(int skip_reading_head)
 {
 	struct worktree **list = NULL;
 	struct strbuf path = STRBUF_INIT;
@@ -128,7 +131,7 @@ struct worktree **get_worktrees(void)
 
 	ALLOC_ARRAY(list, alloc);
 
-	list[counter++] = get_main_worktree();
+	list[counter++] = get_main_worktree(skip_reading_head);
 
 	strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
 	dir = opendir(path.buf);
@@ -137,7 +140,7 @@ struct worktree **get_worktrees(void)
 		while ((d = readdir_skip_dot_and_dotdot(dir)) != NULL) {
 			struct worktree *linked = NULL;
 
-			if ((linked = get_linked_worktree(d->d_name))) {
+			if ((linked = get_linked_worktree(d->d_name, skip_reading_head))) {
 				ALLOC_GROW(list, counter + 1, alloc);
 				list[counter++] = linked;
 			}
@@ -151,6 +154,11 @@ struct worktree **get_worktrees(void)
 	return list;
 }
 
+struct worktree **get_worktrees(void)
+{
+	return get_worktrees_internal(0);
+}
+
 const char *get_worktree_git_dir(const struct worktree *wt)
 {
 	if (!wt)
@@ -591,7 +599,7 @@ static void repair_noop(int iserr UNUSED,
 
 void repair_worktrees(worktree_repair_fn fn, void *cb_data)
 {
-	struct worktree **worktrees = get_worktrees();
+	struct worktree **worktrees = get_worktrees_internal(1);
 	struct worktree **wt = worktrees + 1; /* +1 skips main worktree */
 
 	if (!fn)
-- 
2.43.GIT


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