Address PR review comments

Author: vepadulano

config/rootrc.in

@@ -612,3 +612,8 @@ Rint.Canvas.HighLightColor:      5
 #                          1 All Branches (default)
 # Can be overridden by the environment variable ROOT_TTREECACHE_PREFILL
 # TTreeCache.Prefill: 1
+
+# Set whether to suppress an info message coming from RDataFrame Snapshot
+# informing the user on the change of default output dataset compression
+# settings introduced in ROOT 6.38 (on by default)
+# ROOT.RDF.Snapshot.Info: 1

tree/dataframe/inc/ROOT/RDF/RInterface.hxx

@@ -37,6 +37,7 @@
 #include "ROOT/TypeTraits.hxx"
 #include "RtypesCore.h" // for ULong64_t
 #include "TDirectory.h"
+#include "TEnv.h"
 #include "TH1.h" // For Histo actions
 #include "TH2.h" // For Histo actions
 #include "TH3.h" // For Histo actions
@@ -1341,15 +1342,19 @@ public:
       static_assert(false && "Remove information about change of Snapshot defaut compression settings.");
 #endif
       [[maybe_unused]] static bool once = []() {
-         if (const char *suppress = std::getenv("ROOT_RDF_SILENCE_SNAPSHOT_INFO"))
-            if (std::strcmp(suppress, "1") == 0)
+         if (const char *suppress = std::getenv("ROOT_RDF_SNAPSHOT_INFO"))
+            if (std::strcmp(suppress, "0") == 0)
+               return true;
+         if (const char *suppress = gEnv->GetValue("ROOT.RDF.Snapshot.Info", "1"))
+            if (std::strcmp(suppress, "0") == 0)
                return true;
          RLogScopedVerbosity showInfo{ROOT::Detail::RDF::RDFLogChannel(), ROOT::ELogLevel::kInfo};
          R__LOG_INFO(ROOT::Detail::RDF::RDFLogChannel())
-            << "In ROOT 6.38, the default compression settings of Snapshot have been changed from 101 (ZLIB with "
+            << "\n\tIn ROOT 6.38, the default compression settings of Snapshot have been changed from 101 (ZLIB with "
                "compression level 1, the TTree default) to 505 (ZSTD with compression level 5). This change may result "
                "in smaller Snapshot output dataset size by default. In order to suppress this message, set "
-               "ROOT_RDF_SILENCE_SNAPSHOT_INFO=1 in your environment.";
+               "'ROOT_RDF_SNAPSHOT_INFO=0' in your environment or set 'ROOT.RDF.Snapshot.Info: 0' in your .rootrc "
+               "file.";
          return true;
       }();
       // like columnList but with `#var` columns removed