+Sometimes, you may need to make an override target only run commands when a
+particular package is being built. This can be accomplished using
+L<dh_listpackages(1)> to test what is being built. For example:
+
+ #!/usr/bin/make -f
+ %:
+ dh $@
+
+ override_dh_fixperms:
+ dh_fixperms
+ ifneq (,$(filter foo, $(shell dh_listpackages)))
+ chmod 4755 debian/foo/usr/bin/foo
+ endif
+
+Finally, remember that you are not limited to using override targets in the
+rules file when using B<dh>. You can also explicitly define the regular
+rules file targets when it makes sense to do so. A common reason to do this
+is if your package needs different B<build-arch> and B<build-indep> targets.
+For example, a package with a long document build process can put it in
+B<build-indep>.
+
+ #!/usr/bin/make -f
+ %:
+ dh $@
+
+ binary: binary-arch binary-indep ;
+ binary-arch:: build-arch
+ binary-indep:: build-indep
+ build: build-arch build-indep ;
+ build-indep:
+ $(MAKE) docs
+ build-arch:
+ $(MAKE) bins
+
+=head1 INTERNALS
+
+If you're curious about B<dh>'s internals, here's how it works under the hood.
+
+Each debhelper command will record when it's successfully run in
+F<debian/package.debhelper.log>. (Which B<dh_clean> deletes.) So B<dh> can tell
+which commands have already been run, for which packages, and skip running
+those commands again.
+
+Each time B<dh> is run, it examines the log, and finds the last logged command
+that is in the specified sequence. It then continues with the next command
+in the sequence. The B<--until>, B<--before>, B<--after>, and B<--remaining>
+options can override this behavior.
+
+B<dh> uses the B<DH_INTERNAL_OPTIONS> environment variable to pass information
+through to debhelper commands that are run inside override targets. The
+contents (and indeed, existence) of this environment variable, as the name
+might suggest, is subject to change at any time.
+