Merge branch 'ps/odb-for-each-object' into ps/odb-sources

* ps/odb-for-each-object:
  odb: drop unused `for_each_{loose,packed}_object()` functions
  reachable: convert to use `odb_for_each_object()`
  builtin/pack-objects: use `packfile_store_for_each_object()`
  odb: introduce mtime fields for object info requests
  treewide: drop uses of `for_each_{loose,packed}_object()`
  treewide: enumerate promisor objects via `odb_for_each_object()`
  builtin/fsck: refactor to use `odb_for_each_object()`
  odb: introduce `odb_for_each_object()`
  packfile: introduce function to iterate through objects
  packfile: extract function to iterate through objects of a store
  object-file: introduce function to iterate through objects
  object-file: extract function to read object info from path
  odb: fix flags parameter to be unsigned
  odb: rename `FOR_EACH_OBJECT_*` flags

1 files changed, 52 insertions, 6 deletions

diff --git a/odb.h b/odb.h
index 83d3a37805..2e643de2ee 100644
--- a/odb.h
+++ b/odb.h
@@ -335,6 +335,19 @@ struct object_info {
 	struct object_id *delta_base_oid;
 	void **contentp;
 
+	/*
+	 * The time the given looked-up object has been last modified.
+	 *
+	 * Note: the mtime may be ambiguous in case the object exists multiple
+	 * times in the object database. It is thus _not_ recommended to use
+	 * this field outside of contexts where you would read every instance
+	 * of the object, like for example with `odb_for_each_object()`. As it
+	 * is impossible to say at the ODB level what the intent of the caller
+	 * is (e.g. whether to find the oldest or newest object), it is the
+	 * responsibility of the caller to disambiguate the mtimes.
+	 */
+	time_t *mtimep;
+
 	/* Response */
 	enum {
 		OI_CACHED,
@@ -459,26 +472,59 @@ static inline void obj_read_unlock(void)
 	if(obj_read_use_lock)
 		pthread_mutex_unlock(&obj_read_mutex);
 }
+
 /* Flags for for_each_*_object(). */
-enum for_each_object_flags {
+enum odb_for_each_object_flags {
 	/* Iterate only over local objects, not alternates. */
-	FOR_EACH_OBJECT_LOCAL_ONLY = (1<<0),
+	ODB_FOR_EACH_OBJECT_LOCAL_ONLY = (1<<0),
 
 	/* Only iterate over packs obtained from the promisor remote. */
-	FOR_EACH_OBJECT_PROMISOR_ONLY = (1<<1),
+	ODB_FOR_EACH_OBJECT_PROMISOR_ONLY = (1<<1),
 
 	/*
 	 * Visit objects within a pack in packfile order rather than .idx order
 	 */
-	FOR_EACH_OBJECT_PACK_ORDER = (1<<2),
+	ODB_FOR_EACH_OBJECT_PACK_ORDER = (1<<2),
 
 	/* Only iterate over packs that are not marked as kept in-core. */
-	FOR_EACH_OBJECT_SKIP_IN_CORE_KEPT_PACKS = (1<<3),
+	ODB_FOR_EACH_OBJECT_SKIP_IN_CORE_KEPT_PACKS = (1<<3),
 
 	/* Only iterate over packs that do not have .keep files. */
-	FOR_EACH_OBJECT_SKIP_ON_DISK_KEPT_PACKS = (1<<4),
+	ODB_FOR_EACH_OBJECT_SKIP_ON_DISK_KEPT_PACKS = (1<<4),
 };
 
+/*
+ * A callback function that can be used to iterate through objects. If given,
+ * the optional `oi` parameter will be populated the same as if you would call
+ * `odb_read_object_info()`.
+ *
+ * Returning a non-zero error code will cause iteration to abort. The error
+ * code will be propagated.
+ */
+typedef int (*odb_for_each_object_cb)(const struct object_id *oid,
+				      struct object_info *oi,
+				      void *cb_data);
+
+/*
+ * Iterate through all objects contained in the object database. Note that
+ * objects may be iterated over multiple times in case they are either stored
+ * in different backends or in case they are stored in multiple sources.
+ * If an object info request is given, then the object info will be read and
+ * passed to the callback as if `odb_read_object_info()` was called for the
+ * object.
+ *
+ * Returning a non-zero error code from the callback function will cause
+ * iteration to abort. The error code will be propagated.
+ *
+ * Returns 0 on success, a negative error code in case a failure occurred, or
+ * an arbitrary non-zero error code returned by the callback itself.
+ */
+int odb_for_each_object(struct object_database *odb,
+			const struct object_info *request,
+			odb_for_each_object_cb cb,
+			void *cb_data,
+			unsigned flags);
+
 enum {
 	/*
 	 * By default, `odb_write_object()` does not actually write anything