Fix #374: Route tfenv log output to stderr in terraform shim context

When tfenv auto-installs via the terraform shim (bin/terraform), info
and warn messages were sent to stdout, mixing with terraform output.
This broke piped commands like: terraform version -json | jq

Set TFENV_SHIM_MODE=1 in bin/terraform so bashlog routes info/warn
to stderr in that context. Direct tfenv commands (tfenv install, etc.)
are unaffected — their info output remains on stdout.

Author: Zordrak

bin/terraform

@@ -58,6 +58,12 @@ done;
 # Begin Script Body #
 #####################
 
+# Signal to bashlog that we are in the terraform shim context.
+# All tfenv log output (info, warn) should go to stderr so it does
+# not mix with terraform's stdout and break piped commands like:
+#   terraform version -json | jq
+export TFENV_SHIM_MODE=1;
+
 log 'debug' "program=\"${0##*/}\"";
 
 declare tfenv_path="${TFENV_ROOT}/bin/tfenv";

lib/bashlog.sh

@@ -136,7 +136,13 @@ function log() {
   # Standard Output (Pretty)
   case "${level}" in
     'info'|'warn')
-      echo -e "${std_line}";
+      if [ "${TFENV_SHIM_MODE:-0}" -eq 1 ]; then
+        # In shim mode (bin/terraform), all tfenv output goes to stderr
+        # to avoid corrupting terraform's stdout (e.g. terraform version -json | jq)
+        echo -e "${std_line}" >&2;
+      else
+        echo -e "${std_line}";
+      fi;
       ;;
     'debug')
       if [ "${debug_level}" -gt 0 ]; then