Index: src/add.c
==================================================================
--- src/add.c
+++ src/add.c
@@ -375,10 +375,13 @@
 **    --reset                 Reset the ADDED state of a checkout, such
 **                            that all newly-added (but not yet committed)
 **                            files are no longer added. No flags other
 **                            than --verbose and --dry-run may be used
 **                            with --reset.
+**    --allow-reserved        Permit filenames which are reserved on
+**                            Windows platforms. Such files cannot be
+**                            checked out on Windows, so use with care.
 **
 ** The following options are only valid with --reset:
 **    -v|--verbose            Output information about each --reset file
 **    -n|--dry-run            Display instead of run actions
 **
@@ -391,10 +394,11 @@
   const char *zCleanFlag;    /* The --clean option or clean-glob setting */
   const char *zIgnoreFlag;   /* The --ignore option or ignore-glob setting */
   Glob *pIgnore, *pClean;    /* Ignore everything matching the glob patterns */
   unsigned scanFlags = 0;    /* Flags passed to vfile_scan() */
   int forceFlag;
+  int allowReservedFlag = 0; /* --allow-reserved flag */
 
   if(0!=find_option("reset",0,0)){
     int const verboseFlag = find_option("verbose","v",0)!=0;
     int const dryRunFlag = find_option("dry-run","n",0)!=0;
     db_must_be_within_tree();
@@ -405,10 +409,11 @@
 
   zCleanFlag = find_option("clean",0,1);
   zIgnoreFlag = find_option("ignore",0,1);
   forceFlag = find_option("force","f",0)!=0;
   if( find_option("dotfiles",0,0)!=0 ) scanFlags |= SCAN_ALL;
+  allowReservedFlag = find_option("allow-reserved",0,0)!=0;
 
   /* We should be done with options.. */
   verify_all_options();
 
   db_must_be_within_tree();
@@ -429,17 +434,27 @@
 
   /* Load the names of all files that are to be added into sfile temp table */
   for(i=2; i<g.argc; i++){
     char *zName;
     int isDir;
-    Blob fullName;
+    Blob fullName = empty_blob;
 
     /* file_tree_name() throws a fatal error if g.argv[i] is outside of the
     ** checkout. */
     file_tree_name(g.argv[i], &fullName, 0, 1);
+    if(0==allowReservedFlag
+       && 0!=file_is_win_reserved(blob_str(&fullName))){
+      /* Note that the 'add' internal machinery already _silently_
+      ** skips over any names for which file_is_reserved_name()
+      ** returns true or which is in the fossil_reserved_name()
+      ** list. We do not need to warn for those, as they're outright
+      ** verboten. */
+      fossil_fatal("Filename is reserved: %b\n"
+                   "Use --allow-reserved to permit "
+                   "reserved filenames.", &fullName);
+    }
     blob_reset(&fullName);
-
     file_canonical_name(g.argv[i], &fullName, 0);
     zName = blob_str(&fullName);
     isDir = file_isdir(zName, RepoFILE);
     if( isDir==1 ){
       vfile_scan(&fullName, nRoot-1, scanFlags, pClean, pIgnore, RepoFILE);