odb: move reparenting logic into respective subsystems

The primary object database source may be initialized with a relative
path. When the process changes its current working directory we thus
have to update this path and have it point to the same path, but
relative to the new working directory.

This logic is handled in the object database layer. It consists of three
steps:

  1. We undo any potential temporary object directory, which are used
     for transactions. This is done so that we don't end up modifying
     the temporary object database source that got applied for the
     transaction.

  2. We then iterate through the non-transactional sources and reparent
     their respective paths.

  3. We reapply the temporary object directory, but update its path.

All of this logic is heavily tied to how the object database source
handles paths in the first place. It's an internal implementation
detail, and as sources may not even use an on-disk path at all it is not
a mechanism that applies to all potential sources.

Refactor the code so that the logic to reparent the sources is hosted by
the "files" source and the temporary object directory subsystems,
respectively. This logic is easier to reason about, but it also ensures
that this logic is handled at the correct level.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

odb.c

@@ -1,6 +1,5 @@
 #include "git-compat-util.h"
 #include "abspath.h"
-#include "chdir-notify.h"
 #include "commit-graph.h"
 #include "config.h"
 #include "dir.h"
@@ -1037,38 +1036,6 @@ int odb_write_object_stream(struct object_database *odb,
 	return odb_source_loose_write_stream(odb->sources, stream, len, oid);
 }
 
-static void odb_update_commondir(const char *name UNUSED,
-				 const char *old_cwd,
-				 const char *new_cwd,
-				 void *cb_data)
-{
-	struct object_database *odb = cb_data;
-	struct tmp_objdir *tmp_objdir;
-	struct odb_source *source;
-
-	tmp_objdir = tmp_objdir_unapply_primary_odb();
-
-	/*
-	 * In theory, we only have to do this for the primary object source, as
-	 * alternates' paths are always resolved to an absolute path.
-	 */
-	for (source = odb->sources; source; source = source->next) {
-		char *path;
-
-		if (is_absolute_path(source->path))
-			continue;
-
-		path = reparent_relative_path(old_cwd, new_cwd,
-					      source->path);
-
-		free(source->path);
-		source->path = path;
-	}
-
-	if (tmp_objdir)
-		tmp_objdir_reapply_primary_odb(tmp_objdir, old_cwd, new_cwd);
-}
-
 struct object_database *odb_new(struct repository *repo,
 				const char *primary_source,
 				const char *secondary_sources)
@@ -1089,8 +1056,6 @@ struct object_database *odb_new(struct repository *repo,
 
 	free(to_free);
 
-	chdir_notify_register(NULL, odb_update_commondir, o);
-
 	return o;
 }
 
@@ -1136,8 +1101,6 @@ void odb_free(struct object_database *o)
 
 	string_list_clear(&o->submodule_source_paths, 0);
 
-	chdir_notify_unregister(NULL, odb_update_commondir, o);
-
 	free(o);
 }
 

odb/source-files.c

@@ -1,13 +1,28 @@
 #include "git-compat-util.h"
+#include "abspath.h"
+#include "chdir-notify.h"
 #include "object-file.h"
 #include "odb/source.h"
 #include "odb/source-files.h"
 #include "packfile.h"
 
+static void odb_source_files_reparent(const char *name UNUSED,
+				      const char *old_cwd,
+				      const char *new_cwd,
+				      void *cb_data)
+{
+	struct odb_source_files *files = cb_data;
+	char *path = reparent_relative_path(old_cwd, new_cwd,
+					    files->base.path);
+	free(files->base.path);
+	files->base.path = path;
+}
+
 void odb_source_files_free(struct odb_source_files *files)
 {
 	if (!files)
 		return;
+	chdir_notify_unregister(NULL, odb_source_files_reparent, files);
 	odb_source_loose_free(files->loose);
 	packfile_store_free(files->packed);
 	odb_source_release(&files->base);
@@ -25,5 +40,13 @@ struct odb_source_files *odb_source_files_new(struct object_database *odb,
 	files->loose = odb_source_loose_new(&files->base);
 	files->packed = packfile_store_new(&files->base);
 
+	/*
+	 * Ideally, we would only ever store absolute paths in the source. This
+	 * is not (yet) possible though because we access and assume relative
+	 * paths in the primary ODB source in some user-facing functionality.
+	 */
+	if (!is_absolute_path(path))
+		chdir_notify_register(NULL, odb_source_files_reparent, files);
+
 	return files;
 }

tmp-objdir.c

@@ -36,6 +36,21 @@ static void tmp_objdir_free(struct tmp_objdir *t)
 	free(t);
 }
 
+static void tmp_objdir_reparent(const char *name UNUSED,
+				const char *old_cwd,
+				const char *new_cwd,
+				void *cb_data)
+{
+	struct tmp_objdir *t = cb_data;
+	char *path;
+
+	path = reparent_relative_path(old_cwd, new_cwd,
+				      t->path.buf);
+	strbuf_reset(&t->path);
+	strbuf_addstr(&t->path, path);
+	free(path);
+}
+
 int tmp_objdir_destroy(struct tmp_objdir *t)
 {
 	int err;
@@ -51,6 +66,7 @@ int tmp_objdir_destroy(struct tmp_objdir *t)
 
 	err = remove_dir_recursively(&t->path, 0);
 
+	chdir_notify_unregister(NULL, tmp_objdir_reparent, t);
 	tmp_objdir_free(t);
 
 	return err;
@@ -137,6 +153,9 @@ struct tmp_objdir *tmp_objdir_create(struct repository *r,
 	strbuf_addf(&t->path, "%s/tmp_objdir-%s-XXXXXX",
 		    repo_get_object_directory(r), prefix);
 
+	if (!is_absolute_path(t->path.buf))
+		chdir_notify_register(NULL, tmp_objdir_reparent, t);
+
 	if (!mkdtemp(t->path.buf)) {
 		/* free, not destroy, as we never touched the filesystem */
 		tmp_objdir_free(t);
@@ -315,26 +334,3 @@ void tmp_objdir_replace_primary_odb(struct tmp_objdir *t, int will_destroy)
 							  t->path.buf, will_destroy);
 	t->will_destroy = will_destroy;
 }
-
-struct tmp_objdir *tmp_objdir_unapply_primary_odb(void)
-{
-	if (!the_tmp_objdir || !the_tmp_objdir->prev_source)
-		return NULL;
-
-	odb_restore_primary_source(the_tmp_objdir->repo->objects,
-				   the_tmp_objdir->prev_source, the_tmp_objdir->path.buf);
-	the_tmp_objdir->prev_source = NULL;
-	return the_tmp_objdir;
-}
-
-void tmp_objdir_reapply_primary_odb(struct tmp_objdir *t, const char *old_cwd,
-		const char *new_cwd)
-{
-	char *path;
-
-	path = reparent_relative_path(old_cwd, new_cwd, t->path.buf);
-	strbuf_reset(&t->path);
-	strbuf_addstr(&t->path, path);
-	free(path);
-	tmp_objdir_replace_primary_odb(t, t->will_destroy);
-}

tmp-objdir.h

@@ -68,19 +68,4 @@ void tmp_objdir_add_as_alternate(const struct tmp_objdir *);
  */
 void tmp_objdir_replace_primary_odb(struct tmp_objdir *, int will_destroy);
 
-/*
- * If the primary object database was replaced by a temporary object directory,
- * restore it to its original value while keeping the directory contents around.
- * Returns NULL if the primary object database was not replaced.
- */
-struct tmp_objdir *tmp_objdir_unapply_primary_odb(void);
-
-/*
- * Reapplies the former primary temporary object database, after potentially
- * changing its relative path.
- */
-void tmp_objdir_reapply_primary_odb(struct tmp_objdir *, const char *old_cwd,
-		const char *new_cwd);
-
-
 #endif /* TMP_OBJDIR_H */