patch 8.1.0556: saving/restoring search patterns share saved last_idx

Problem:    Saving/restoring search patterns share saved last_idx.
Solution:   Use a separate saved last_idx for saving search patterns for
            functions and incremental search.

src/search.c

@@ -93,12 +93,8 @@ static int	lastc_bytelen = 1;	/* >1 for multi-byte char */
 /* copy of spats[], for keeping the search patterns while executing autocmds */
 static struct spat  saved_spats[2];
 # ifdef FEAT_SEARCH_EXTRA
-/* copy of spats[RE_SEARCH], for keeping the search patterns while incremental
- * searching */
-static struct spat  saved_last_search_spat;
-static int	    did_save_last_search_spat = 0;
-static int	    saved_last_idx = 0;
-static int	    saved_no_hlsearch = 0;
+static int	    saved_spats_last_idx = 0;
+static int	    saved_spats_no_hlsearch = 0;
 # endif
 
 static char_u	    *mr_pattern = NULL;	/* pattern used by search_regcomp() */
@@ -310,8 +306,8 @@ save_search_patterns(void)
 	if (spats[1].pat != NULL)
 	    saved_spats[1].pat = vim_strsave(spats[1].pat);
 #ifdef FEAT_SEARCH_EXTRA
-	saved_last_idx = last_idx;
-	saved_no_hlsearch = no_hlsearch;
+	saved_spats_last_idx = last_idx;
+	saved_spats_no_hlsearch = no_hlsearch;
 #endif
     }
 }
@@ -329,8 +325,8 @@ restore_search_patterns(void)
 	vim_free(spats[1].pat);
 	spats[1] = saved_spats[1];
 #ifdef FEAT_SEARCH_EXTRA
-	last_idx = saved_last_idx;
-	set_no_hlsearch(saved_no_hlsearch);
+	last_idx = saved_spats_last_idx;
+	set_no_hlsearch(saved_spats_no_hlsearch);
 #endif
     }
 }
@@ -354,6 +350,13 @@ free_search_patterns(void)
 #endif
 
 #ifdef FEAT_SEARCH_EXTRA
+// copy of spats[RE_SEARCH], for keeping the search patterns while incremental
+// searching
+static struct spat  saved_last_search_spat;
+static int	    did_save_last_search_spat = 0;
+static int	    saved_last_idx = 0;
+static int	    saved_no_hlsearch = 0;
+
 /*
  * Save and restore the search pattern for incremental highlight search
  * feature.
@@ -575,7 +578,7 @@ set_last_search_pat(
 	    saved_spats[idx].pat = NULL;
 	else
 	    saved_spats[idx].pat = vim_strsave(spats[idx].pat);
-	saved_last_idx = last_idx;
+	saved_spats_last_idx = last_idx;
     }
 # ifdef FEAT_SEARCH_EXTRA
     /* If 'hlsearch' set and search pat changed: need redraw. */

src/version.c

@@ -792,6 +792,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    556,
 /**/
     555,
 /**/