krebs.build: use $F5 to prefix verbose commands

Makefile

@@ -51,7 +51,7 @@ evaluate = \
 execute = \
 	result=$$($(call evaluate,-A config.krebs.build.$(1) --json)) && \
 	script=$$(echo "$$result" | jq -r .) && \
-	echo "$$script" | sh
+	echo "$$script" | PS5=% sh
 
 # usage: make deploy system=foo [target_host=bar]
 deploy: ssh ?= ssh

krebs/3modules/build.nix

@@ -42,12 +42,13 @@ let
           set -eu
 
           verbose() {
-            printf '+%s\n' "$(printf ' %q' "$@")" >&2
+            printf '%s%s\n' "$PS5$(printf ' %q' "$@")" >&2
             "$@"
           }
 
-          echo ${shell.escape git-script} \
-            | ssh -p ${shell.escape target-port} \
+          { printf 'PS5=%q%q\n' @ "$PS5"
+            echo ${shell.escape git-script}
+          } | verbose ssh -p ${shell.escape target-port} \
                   ${shell.escape "${target-user}@${target-host}"} -T
 
           unset tmpdir
@@ -86,7 +87,7 @@ let
           set -efu
 
           verbose() {
-            printf '+%s\n' "$(printf ' %q' "$@")" >&2
+            printf '%s%s\n' "$PS5$(printf ' %q' "$@")" >&2
             "$@"
           }