[diff] set reactive when `infer-diff` is invoked

Summary: Automatically set --reactive because the diff analysis will be faster that way.

Reviewed By: jeremydubreil

Differential Revision: D5499443

fbshipit-source-id: 1a35cee

infer/src/base/Config.ml

@@ -2097,7 +2097,7 @@ and quandary_sinks = !quandary_sinks
 
 and quiet = !quiet
 
-and reactive_mode = !reactive
+and reactive_mode = !reactive || CLOpt.(equal_command Diff) command
 
 and reactive_capture = !reactive_capture
 

infer/src/integration/Diff.ml

@@ -48,16 +48,15 @@ let diff driver_mode =
   (* TODO(t15553258) run gen-build script if specified *)
   (* run capture *)
   Driver.capture driver_mode ~changed_files:None ;
-  (* run analysis TODO(t15553258) add --reactive and --changed_files_index *)
+  (* run analysis TODO(t15553258) add --changed_files_index *)
   Driver.analyze_and_report driver_mode ~changed_files:None ;
   let current_report = Some (save_report Current) in
   (* TODO(t15553258) bail if nothing to analyze (configurable, some people might care about bugs
      fixed more than about time to analyze) *)
   checkout Previous ;
   (* TODO(t15553258) run gen-build script if specified *)
-  (* run capture TODO(t15553258) add --reactive and --continue *)
   Driver.capture driver_mode ~changed_files:None ;
-  (* run analysis TODO(t15553258) add --reactive and --changed_files_index *)
+  (* run analysis TODO(t15553258) add --changed_files_index *)
   Driver.analyze_and_report driver_mode ~changed_files:None ;
   checkout Current ;
   let previous_report = Some (save_report Previous) in