Tweaks to CLI, bugfix for escape replacements

bpeg.c

@@ -86,10 +86,7 @@ int main(int argc, char *argv[])
         } else if (FLAG("--verbose") || FLAG("-v")) {
             verbose = 1;
         } else if (FLAG("--pattern") || FLAG("-p")) {
-            vm_op_t *p = bpeg_pattern(flag);
-            check(p, "Pattern failed to compile");
-            add_def(g, flag, "pattern", p);
-            ++npatterns;
+            rule = flag;
         } else if (FLAG("--replace") || FLAG("-r")) {
             vm_op_t *p = bpeg_replacement(bpeg_pattern("pattern"), flag);
             check(p, "Replacement failed to compile");
@@ -126,7 +123,7 @@ int main(int argc, char *argv[])
     }
 
     vm_op_t *pattern = lookup(g, rule);
-    check(pattern != NULL, usage);
+    check(pattern != NULL, "No such rule: '%s'", rule);
 
     if (verbose) {
         print_pattern(pattern);

grammar.c

@@ -13,6 +13,7 @@ const char *BPEG_BUILTIN_GRAMMAR = (
     "replace-all = *&&@replacement &&$$;\n"
     "find-all = *(matching-line / {&&(\\n/$$)=>});\n"
     "matching-line = +&@pattern *. $ ?\\n;\n"
+    "only-matches = *{&&@pattern=>'@1\\n'};\n"
 
     // Helper definitions (commonly used)
     "crlf=\\r\\n;\n"

vm.c

@@ -377,6 +377,7 @@ void print_match(match_t *m, const char *color, int verbose)
         printf("\033[0;34m");
         for (const char *r = m->name_or_replacement; *r; ) {
             if (*r == '\\') {
+                ++r;
                 fputc(unescapechar(r, &r), stdout);
                 continue;
             } else if (*r != '@') {