maint.mk: a "release-commit" wrapper to do-release-commit-and-tag * build-aux/do-release-commit-and-tag: Move variable definitions together. ($branch): Instead of defaulting to "master", default to the current branch (as gnu-web-doc-update does). (help): Display the current values of the option arguments. * top/maint.mk (release-commit): New. * top/README-release: Simplify the corresponding step.