__single_binary_service: envvars and user-reuse support

The new --env flag allows type users to pass env files that will be
used to setup environment variables on both sytemd and runit.

While there, also solve a minor issue where users managed by this type
could not be re-used for multiple services.

type/__single_binary_service/man.rst

@@ -90,6 +90,11 @@ binary
     If `--unpack` is used, a binary with this name must be unpacked.
     Otherwise, the contents of `--url` will be placed under this binary name.
 
+env
+    An `env` file consiting of `ENVIRONMENT_VARIABLE=VALUE`, one variable per
+    line.
+    Empty lines and those starting with `#` are ignored.
+
 service-args
     Any extra arguments to pass along with `--service-exec`. Beware that any
     service-args having the format `--config=/etc/foo.cfg` should be

type/__single_binary_service/manifest

@@ -112,7 +112,7 @@ if [ "${USER}" != "root" ] && \
 		--system \
 		--state "${STATE}" \
 		--home "${USER_HOME_DIR}" \
-		--comment "cdist-managed ${SERVICE_NAME} user" \
+		--comment "cdist-managed service user" \
 		${USER_CREATE_HOME}
 	# Track dependencies
 	service_require="${service_require} __user/${USER}"
@@ -136,11 +136,21 @@ fi
 
 
 
+# These messages will trigger a service restart (overridden for systemd)
+service_config_reload_pattern="^__file${CONFIG_FILE_DEST}"
+
 # This should setup the object in $service_definition_require
 # See above.
 case "${INIT}" in
 	systemd)
 		if [ -z "${SERVICE_DEFINITION}" ]; then
+			SYSTEMD_ENV_FILE="/etc/systemd/system/${SERVICE_NAME}.env"
+			__file "${SYSTEMD_ENV_FILE}" \
+				--mode 0400 \
+				--source "${__object}/parameter/env"
+			# We need to take into account the envionment file for systemd too
+			service_config_reload_pattern="(${service_config_reload_pattern}|^__file${SYSTEMD_ENV_FILE})"
+
 			SERVICE_DEFINITION="$(cat <<EOF
 [Unit]
 Description=${SERVICE_DESCRIPTION}
@@ -153,6 +163,7 @@ User=${USER}
 Group=${GROUP}
 ExecStart=${SERVICE_EXEC}
 Restart=always
+EnvironmentFile=${SYSTEMD_ENV_FILE}
 ${WORKING_DIRECTORY_SYSTEMD}
 
 [Install]
@@ -169,12 +180,18 @@ EOF
 	;;
 	runit|sysvinit)
 		if [ -z "${SERVICE_DEFINITION}" ]; then
+			RUNIT_ENV="$(sed -Ee 's!^([[:alnum:]_]+)=(.*)$!export \1=\2!' "${__object}/parameter/env")"
 			SERVICE_DEFINITION="$(cat <<EOF
 #!/bin/sh -e
 ${WORKING_DIRECTORY_RUNIT}
+# User-provided environment
+${RUNIT_ENV}
+# System vars
 export HOME="\$(getent passwd '${USER}' | cut -d: -f6)"
 export USER="${USER}"
 export GROUP="${GROUP}"
+
+exec 2>&1
 exec chpst -u "${USER}:${GROUP}" ${SERVICE_EXEC}
 EOF
 )"
@@ -279,10 +296,10 @@ EOF
 			--onchange "${perform_service_upgrade}" \
 			--source "-"
 else
-	# We only restart here if there was a config change
+	# We only restart here if there was a config or env change
 	# but there was not a version change
 	require="${service_require}" __check_messages \
 		"single_binary_service_${__object_id}" \
-		--pattern "^__file${CONFIG_FILE_DEST}" \
+		--pattern "${service_config_reload_pattern}" \
 		--execute "$(sv_cmd restart)"
 fi

type/__single_binary_service/parameter/optional

@@ -1,4 +1,5 @@
 config-file-source
+env
 user
 group
 state