Allow user to define which package need to be installed before tagging.

This is for supporting tagging software collections (SC), if you have
installed meta package of SC then then name of package is different.
I.e. if you are tagging rubygem-foo package and you have ruby193-build
installed then the name of package is ruby193-rubygem-foo.

src/tito/tagger.py

@@ -16,6 +16,7 @@ Code for tagging Spacewalk/Satellite packages.
 
 import os
 import re
+import rpm
 import commands
 import StringIO
 import shutil
@@ -92,12 +93,28 @@ class VersionTagger(object):
         if options.use_version:
             self._use_version = options.use_version
 
+        self.check_tag_precondition()
+
         # Only two paths through the tagger module right now:
         if options.undo:
             self._undo()
         else:
             self._tag_release()
 
+    def check_tag_precondition(self):
+        if self.config.has_option("tagconfig", "require_package"):
+            packages = self.config.get_option("taggerconfig", "require_package").split(',')
+            ts = rpm.TransactionSet()
+            missing_packages = []
+            for p in packages:
+                p = p.strip()
+                mi = ts.dbMatch('name', p)
+                if not mi:
+                    missing_packages.append(p)
+            if missing_packages:
+                raise TitoException("To tag this package, you must first install: %s"
+                    ', '.join(missing_packages))
+
     def _tag_release(self):
         """
         Tag a new version of the package. (i.e. x.y.z+1)

tito.props.5.asciidoc

@@ -108,6 +108,11 @@ REQUIREMENTS
 tito::
 If tito is older then specified version, it will refuse to continue.
 
+TAGCONFIG
+---------
+require_package::
+Comma separated list of packages, which needs to be installed prior tagging. If those
+packages are not installed, tito will refuse to continue.
 
 BUILDERS
 --------

tito.spec

@@ -25,6 +25,7 @@ Requires: fedpkg
 Requires: fedora-cert
 Requires: fedora-packager
 Requires: rpmdevtools
+Requires: rpm-python
 
 %description
 Tito is a tool for managing tarballs, rpms, and builds for projects using