curl: add --fail-early

Exit with an error on the first transfer error instead of continuing to
do the rest of the URLs.

Discussion: https://curl.haxx.se/mail/archive-2016-11/0038.html

src/tool_cfgable.h

@@ -239,7 +239,7 @@ struct GlobalConfig {
   bool tracetime;                 /* include timestamp? */
   int progressmode;               /* CURL_PROGRESS_BAR / CURL_PROGRESS_STATS */
   char *libcurl;                  /* Output libcurl code to this file name */
-
+  bool fail_early;                /* exit on first transfer error */
   struct OperationConfig *first;
   struct OperationConfig *current;
   struct OperationConfig *last;   /* Always last in the struct */

src/tool_getparam.c

@@ -231,6 +231,7 @@ static const struct LongShort aliases[]= {
   {"Es", "ssl-no-revoke",            FALSE},
   {"Et", "tcp-fastopen",             FALSE},
   {"f",  "fail",                     FALSE},
+  {"fa", "fail-early",               FALSE},
   {"F",  "form",                     TRUE},
   {"Fs", "form-string",              TRUE},
   {"g",  "globoff",                  FALSE},
@@ -1438,8 +1439,14 @@ ParameterError getparameter(char *flag,    /* f or -long-flag */
       }
       break;
     case 'f':
-      /* fail hard on errors  */
-      config->failonerror = toggle;
+      switch(subletter) {
+      case 'a': /* --fail-early */
+        global->fail_early = toggle;
+        break;
+      default:
+        /* fail hard on errors  */
+        config->failonerror = toggle;
+      }
       break;
     case 'F':
       /* "form data" simulation, this is a little advanced so lets do our best

src/tool_operate.c

@@ -1805,9 +1805,9 @@ static CURLcode operate_do(struct GlobalConfig *global,
     urlnode->flags = 0;
 
     /*
-    ** Bail out upon critical errors
+    ** Bail out upon critical errors or --fail-early
     */
-    if(is_fatal_error(result))
+    if(is_fatal_error(result) || (result && global->fail_early))
       goto quit_curl;
 
   } /* for-loop through all URLs */