After much pain and suffering, finally tracked down all the places that

the timestamp is updated after reading in CIF or GDS, and managed to
get the timestamp dirty flag to remain clear after reading when
"gds datestamp" is used.  This includes a modification of the timestamp
update routine that only updates timestamps on a single file if only a
single file is being written.

calma/CalmaRdcl.c

@@ -550,11 +550,11 @@ calmaParseStructure(filename)
 
     DBWAreaChanged(cifReadCellDef, &cifReadCellDef->cd_bbox,
 	DBW_ALLWINDOWS, &DBAllButSpaceBits);
-    DBCellSetModified(cifReadCellDef, TRUE);
 
-    /* Only mark cell as needing a timestamp update if the timestamp is zero */
-    if (cifReadCellDef->cd_timestamp != 0)
-	cifReadCellDef->cd_flags &= ~CDGETNEWSTAMP;
+    /* Note:  This sets the CDGETNEWSTAMP flag, but if the timestamp is
+     * not zero, then it gets cleared in CIFReadCellCleanup().
+     */
+    DBCellSetModified(cifReadCellDef, TRUE);
 
     /*
      * Assign use-identifiers to all the cell uses.

cif/CIFrdcl.c

@@ -1660,6 +1660,10 @@ CIFReadCellCleanup(filetype)
 	    DRCCheckThis(def, TT_CHECKPAINT, &def->cd_bbox);
 	DBWAreaChanged(def, &def->cd_bbox, DBW_ALLWINDOWS, &DBAllButSpaceBits);
 	DBCellSetModified(def, TRUE);
+
+	/* Only mark cell as needing a timestamp update if the timestamp is zero */
+	if (def->cd_timestamp != 0)
+	    def->cd_flags &= ~CDGETNEWSTAMP;
     }
 
     /* Do geometrical processing on the top-level cell. */

commands/CmdRS.c

@@ -209,7 +209,7 @@ CmdSave(w, cmd)
     else
 	locDef = EditCellUse->cu_def;
 
-    DBUpdateStamps();
+    DBUpdateStamps(locDef);
     if (cmd->tx_argc == 2)
     {
 	char *fileName;
@@ -1151,7 +1151,7 @@ CmdSelect(w, cmd)
 		    DBStdPaintTbl(TT_CHECKPAINT, PL_DRC_CHECK),
 		    (PaintUndoInfo *) NULL);
 
-	    DBUpdateStamps();
+	    DBUpdateStamps(SelectDef);
 	    cmdSaveCell(SelectDef, cmd->tx_argv[2], FALSE, FALSE);
 	    return;
 

commands/CmdSubrs.c

@@ -637,7 +637,7 @@ cmdSaveCell(cellDef, newName, noninteractive, tryRename)
 	}
     }
 
-    DBUpdateStamps();
+    DBUpdateStamps(cellDef);
     if (!DBCellWrite(cellDef, fileName))
     {
 	TxError("Could not write file.  Cell not written.\n");

commands/CmdTZ.c

@@ -1837,21 +1837,26 @@ CmdWriteall(w, cmd)
 	/* Check if all cells exist */
 	if (cmd->tx_argc > 2)
 	{
+	    CellDef *def;
 	    int i;
 	    int notfound = 0;
 	    for (i = 2; i < cmd->tx_argc; i++)
 	    {
-		if (DBCellLookDef(cmd->tx_argv[i]) == NULL)
+		def = DBCellLookDef(cmd->tx_argv[i]);
+		if (def == NULL)
 		{
 		    TxError("No such cell \"%s\".\n", cmd->tx_argv[i]);
 		    notfound++;
 		}
+		else if (option != OPT_WRITEALL_NOUPDATE)
+		    DBUpdateStamps(def);
 	    }
 	    if (notfound == cmd->tx_argc - 2) return;
 	}
     }
     if (option != OPT_WRITEALL_NOUPDATE)
-	DBUpdateStamps();
+	if (cmd->tx_argc <= 2)
+	    DBUpdateStamps(NULL);
 
     argc = cmd->tx_argc;
     (void) DBCellSrDefs(flags, cmdWriteallFunc, (ClientData)cmd);

database/DBcellsrch.c

@@ -1511,8 +1511,6 @@ DBScaleEverything(scalen, scaled)
     int dbCellDefEnumFunc();
     LinkedCellDef *lhead, *lcd;
 
-    // DBUpdateStamps();
-
     SigDisableInterrupts();
 
     lhead = NULL;

database/DBtimestmp.c

@@ -207,14 +207,18 @@ DBFixMismatch()
  */
 
 void
-DBUpdateStamps()
+DBUpdateStamps(def)
+    CellDef *def;
 {
     extern int dbStampFunc();
     extern time_t time();
 
     DBFixMismatch();
     timestamp = time((time_t *) 0);
-    (void) DBCellSrDefs(CDGETNEWSTAMP, dbStampFunc, (ClientData) NULL);
+    if (def == NULL)
+	(void) DBCellSrDefs(CDGETNEWSTAMP, dbStampFunc, (ClientData) NULL);
+    else if (def->cd_flags & CDGETNEWSTAMP)
+	dbStampFunc(def);
 }
 
 int

extract/ExtMain.c

@@ -553,7 +553,7 @@ ExtIncremental(rootUse)
     DBFixMismatch();
 
     /* Update all timestamps */
-    DBUpdateStamps();
+    DBUpdateStamps(NULL);
 
     /* Mark all defs as being unvisited */
     (void) DBCellSrDefs(0, extDefInitFunc, (ClientData) 0);