sha1-file: introduce no-lazy-fetch has_object()

There have been a few bugs wherein Git fetches missing objects whenever
the existence of an object is checked, even though it does not need to
perform such a fetch. To resolve these bugs, we could look at all the
places that has_object_file() (or a similar function) is used. As a
first step, introduce a new function has_object() that checks for the
existence of an object, with a default behavior of not fetching if the
object is missing and the repository is a partial clone. As we verify
each has_object_file() (or similar) usage, we can replace it with
has_object(), and we will know that we are done when we can delete
has_object_file() (and the other similar functions).

Also, the new function has_object() has more appropriate defaults:
besides not fetching, it also does not recheck packed storage.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 23 insertions, 2 deletions

diff --git a/object-store.h b/object-store.h
index f439d47..c4fc9dd 100644
--- a/object-store.h
+++ b/object-store.h
@@ -239,12 +239,33 @@ int read_loose_object(const char *path,
 		      unsigned long *size,
 		      void **contents);
 
+/* Retry packed storage after checking packed and loose storage */
+#define HAS_OBJECT_RECHECK_PACKED 1
+
+/*
+ * Returns 1 if the object exists. This function will not lazily fetch objects
+ * in a partial clone.
+ */
+int has_object(struct repository *r, const struct object_id *oid,
+	       unsigned flags);
+
+/*
+ * These macros and functions are deprecated. If checking existence for an
+ * object that is likely to be missing and/or whose absence is relatively
+ * inconsequential (or is consequential but the caller is prepared to handle
+ * it), use has_object(), which has better defaults (no lazy fetch in a partial
+ * clone and no rechecking of packed storage). In the unlikely event that a
+ * caller needs to assert existence of an object that it fully expects to
+ * exist, and wants to trigger a lazy fetch in a partial clone, use
+ * oid_object_info_extended() with a NULL struct object_info.
+ *
+ * These functions can be removed once all callers have migrated to
+ * has_object() and/or oid_object_info_extended().
+ */
 #ifndef NO_THE_REPOSITORY_COMPATIBILITY_MACROS
 #define has_sha1_file_with_flags(sha1, flags) repo_has_sha1_file_with_flags(the_repository, sha1, flags)
 #define has_sha1_file(sha1) repo_has_sha1_file(the_repository, sha1)
 #endif
-
-/* Same as the above, except for struct object_id. */
 int repo_has_object_file(struct repository *r, const struct object_id *oid);
 int repo_has_object_file_with_flags(struct repository *r,
 				    const struct object_id *oid, int flags);