Replace 44 ad-hoc shell test scripts with 223 bats tests across 11 files:

- alt.bats (39): set_target_type, get_altdistr_*, get_type_by_git_branch_name
- spec_release.bats (50): get_numrelease, get_txtrelease, decrement_release,
  inc_release, inc_subrelease, reset_release, MAJOR/MINOR parsing
- spec.bats (25): get_numpartrelease, is_backported_release, separate_changelog,
  get_var, prevprelease, remove_bashism
- strings.bats (36): rhas, isnumber, drop_args, initial_letter, is_dirpath,
  is_absolute_path, sed escaping
- common.bats (15): usearg, version_more_version, stripcolors, is_ssh_target
- git.bats (23): version_to_tag, tag_to_version, normalize_girar_name,
  is_girar_name
- integration.bats (10): tolocal_anyrepl for various distros, filter_deb_pkgnames
- rpm.bats (10): get_pkgname_from_filename
- repl.bats (6): perl regex package name replacement
- docmd.bats (5): showcmd, docmd
- bash.bats (5): shell variable scoping behavior

Add Makefile targets: make test, make test-verbose