avoid unnecessary cleanups of recovery files

* After the last commit 0b593eb7d0e6907b19cdbb605caf1becae351004
  we tried to clean up (unlink) recovery files for all dirty buffers.
  This resulted in superfluous file deletions before any recovery
  file was dumped; after disabling file recovery and even in
  batch mode.
  It's not tolerable that SciTECO scripts try to unlink files
  as a side effect e.g. of EW.
  Also, sometimes you may have to clean up recovery dumps even
  in batch mode, e.g. in Quit hooks.
* Also, it was broken for dirty unnamed buffers, which would
  cause glib errors.
* That's why we had to add another buffer state for
  dirty files with outdated recovery dumps (TECO_BUFFER_DIRTY_OUTDATED_DUMP).
  Once a dump was written, a buffer never directly transitions
  into the TECO_BUFFER_DIRTY_NO_DUMP state again.
  We can now reliably unlink() only where we'd expect a
  recovery file to exist in the first place.

1 files changed, 6 insertions, 4 deletions

diff --git a/src/ring.h b/src/ring.h
index 4624983..d81c3db 100644
--- a/src/ring.h
+++ b/src/ring.h
@@ -28,10 +28,12 @@
 typedef enum {
 	/** buffer is freshly opened or saved */
 	TECO_BUFFER_CLEAN = 0,
-	/** buffer modified - if a recovery file already exists, it is outdated */
-	TECO_BUFFER_DIRTY,
-	/** buffer modified and recovery file already written */
-	TECO_BUFFER_DIRTY_DUMPED
+	/** buffer modified, but a recovery file does not yet exist */
+	TECO_BUFFER_DIRTY_NO_DUMP,
+	/** buffer modified, recovery file outdated */
+	TECO_BUFFER_DIRTY_OUTDATED_DUMP,
+	/** buffer modified and recovery file is up to date */
+	TECO_BUFFER_DIRTY_RECENT_DUMP
 } teco_buffer_state_t;
 
 typedef struct teco_buffer_t {