add $si command

src/Revision-generate.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+GIT_REVISION_HASH=$(git rev-parse --short HEAD)
+TIMESTAMP_SECS=$(date +%s)
+
+if [ -z "$GIT_REVISION_HASH" ]; then
+  GIT_REVISION_HASH="????"
+else
+  if ! git diff-index --quiet HEAD -- ; then
+    GIT_REVISION_HASH="$GIT_REVISION_HASH+"
+  fi
+fi
+
+cat > Revision.cc <<EOF
+#include "Revision.hh"
+
+const char* GIT_REVISION_HASH = "$GIT_REVISION_HASH";
+const uint64_t BUILD_TIMESTAMP = static_cast<uint64_t>($TIMESTAMP_SECS) * 1000000;
+EOF