odb: split struct odb_transaction into separate header

The current ODB transaction interface is colocated with other ODB
interfaces in "odb.{c,h}". Subsequent commits will expand `struct
odb_transaction` to support write operations on the transaction
directly. To keep things organized and prevent "odb.{c,h}" from becoming
more unwieldy, split out `struct odb_transaction` into a separate
header.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: jltobler

Makefile

@@ -1219,6 +1219,7 @@ LIB_OBJS += odb.o
 LIB_OBJS += odb/source.o
 LIB_OBJS += odb/source-files.o
 LIB_OBJS += odb/streaming.o
+LIB_OBJS += odb/transaction.o
 LIB_OBJS += oid-array.o
 LIB_OBJS += oidmap.o
 LIB_OBJS += oidset.o

builtin/add.c

@@ -16,6 +16,7 @@
 #include "run-command.h"
 #include "object-file.h"
 #include "odb.h"
+#include "odb/transaction.h"
 #include "parse-options.h"
 #include "path.h"
 #include "preload-index.h"

builtin/unpack-objects.c

@@ -9,6 +9,7 @@
 #include "hex.h"
 #include "object-file.h"
 #include "odb.h"
+#include "odb/transaction.h"
 #include "object.h"
 #include "delta.h"
 #include "pack.h"

builtin/update-index.c

@@ -19,6 +19,7 @@
 #include "tree-walk.h"
 #include "object-file.h"
 #include "odb.h"
+#include "odb/transaction.h"
 #include "refs.h"
 #include "resolve-undo.h"
 #include "parse-options.h"

cache-tree.c

@@ -10,6 +10,7 @@
 #include "cache-tree.h"
 #include "object-file.h"
 #include "odb.h"
+#include "odb/transaction.h"
 #include "read-cache-ll.h"
 #include "replace-object.h"
 #include "repository.h"

meson.build

@@ -405,6 +405,7 @@ libgit_sources = [
   'odb/source.c',
   'odb/source-files.c',
   'odb/streaming.c',
+  'odb/transaction.c',
   'oid-array.c',
   'oidmap.c',
   'oidset.c',

object-file.c

@@ -21,6 +21,7 @@
 #include "object-file.h"
 #include "odb.h"
 #include "odb/streaming.h"
+#include "odb/transaction.h"
 #include "oidtree.h"
 #include "pack.h"
 #include "packfile.h"

odb.c

@@ -1069,28 +1069,3 @@ void odb_reprepare(struct object_database *o)
 
 	obj_read_unlock();
 }
-
-struct odb_transaction *odb_transaction_begin(struct object_database *odb)
-{
-	if (odb->transaction)
-		return NULL;
-
-	odb->transaction = odb_transaction_files_begin(odb->sources);
-
-	return odb->transaction;
-}
-
-void odb_transaction_commit(struct odb_transaction *transaction)
-{
-	if (!transaction)
-		return;
-
-	/*
-	 * Ensure the transaction ending matches the pending transaction.
-	 */
-	ASSERT(transaction == transaction->source->odb->transaction);
-
-	transaction->commit(transaction);
-	transaction->source->odb->transaction = NULL;
-	free(transaction);
-}

odb.h

@@ -35,24 +35,6 @@ struct packed_git;
 struct packfile_store;
 struct cached_object_entry;
 
-/*
- * A transaction may be started for an object database prior to writing new
- * objects via odb_transaction_begin(). These objects are not committed until
- * odb_transaction_commit() is invoked. Only a single transaction may be pending
- * at a time.
- *
- * Each ODB source is expected to implement its own transaction handling.
- */
-struct odb_transaction;
-typedef void (*odb_transaction_commit_fn)(struct odb_transaction *transaction);
-struct odb_transaction {
-	/* The ODB source the transaction is opened against. */
-	struct odb_source *source;
-
-	/* The ODB source specific callback invoked to commit a transaction. */
-	odb_transaction_commit_fn commit;
-};
-
 /*
  * The object database encapsulates access to objects in a repository. It
  * manages one or more sources that store the actual objects which are
@@ -154,19 +136,6 @@ void odb_close(struct object_database *o);
  */
 void odb_reprepare(struct object_database *o);
 
-/*
- * Starts an ODB transaction. Subsequent objects are written to the transaction
- * and not committed until odb_transaction_commit() is invoked on the
- * transaction. If the ODB already has a pending transaction, NULL is returned.
- */
-struct odb_transaction *odb_transaction_begin(struct object_database *odb);
-
-/*
- * Commits an ODB transaction making the written objects visible. If the
- * specified transaction is NULL, the function is a no-op.
- */
-void odb_transaction_commit(struct odb_transaction *transaction);
-
 /*
  * Find source by its object directory path. Returns a `NULL` pointer in case
  * the source could not be found.

odb/transaction.c

@@ -0,0 +1,28 @@
+#include "git-compat-util.h"
+#include "object-file.h"
+#include "odb/transaction.h"
+
+struct odb_transaction *odb_transaction_begin(struct object_database *odb)
+{
+	if (odb->transaction)
+		return NULL;
+
+	odb->transaction = odb_transaction_files_begin(odb->sources);
+
+	return odb->transaction;
+}
+
+void odb_transaction_commit(struct odb_transaction *transaction)
+{
+	if (!transaction)
+		return;
+
+	/*
+	 * Ensure the transaction ending matches the pending transaction.
+	 */
+	ASSERT(transaction == transaction->source->odb->transaction);
+
+	transaction->commit(transaction);
+	transaction->source->odb->transaction = NULL;
+	free(transaction);
+}