Unity Script Reference:
Legacy Documentation: Version 4.3.0
AssetModificationProcessorNamespace: UnityEditor
Description

AssetModificationProcessor lets you hook into saving of serialized assets and scenes which are edited inside Unity.

This lets you prevent writing of assets by Unity for integration with VCS solutions like Perforce which require locking of files.
Messages
IsOpenForEdit This is called by Unity when inspecting an asset to determine if an editor should be disabled.
OnWillCreateAsset This is called by Unity when it is about to create an asset not imported by the user, eg. ".meta" files.
OnWillDeleteAsset This is called by Unity when it is about to delete an asset from disk.
OnWillMoveAsset This is called by Unity when it is about to move an asset on disk.
OnWillSaveAssets This is called by Unity when it is about to write serialized assets or scene files to disk.