Document %clean as obsolete and drop the unnecessary default %clean

In rpm < 4.8, %clean was needed to clean up the build root for packages
that used one (it was optional before 4.6). Since the introduction of
the new %builddir in 9d35c8d,
everything the package produces is collected in that one directory
that we can and do centrally clean up, making the separate %clean
section even more useless.

Document %clean as obsolete and drop all the now unnecessary default
%clean sections we've been adding for the packages.

build/parseSpec.c

@@ -1267,13 +1267,6 @@ static rpmSpec parseSpec(const char *specFile, rpmSpecFlags flags,
     if (parseSpecSection(&spec, PARSE_SPECFILE) != RPMRC_OK)
 	goto errxit;
 
-    if (spec->sections[SECT_CLEAN] == NULL) {
-	char *body = rpmExpand("%{buildsystem_default_clean}", NULL);
-	spec->sections[SECT_CLEAN] = newStringBuf();
-	appendLineStringBuf(spec->sections[SECT_CLEAN], body);
-	free(body);
-    }
-
     /* Assemble source header from parsed components */
     initSourceHeader(spec);
     return spec;

docs/manual/spec.md

@@ -664,6 +664,12 @@ places. For many simple packages this is just:
 If the packaged software has accomppanying tests, this is where they
 should be executed.
 
+### %clean (OBSOLETE)
+
+Packages should place all their temporaries inside their designated
+`%builddir`, which rpm will automatically clean up. Needing a package
+specific `%clean` section generally suggests flaws in the spec.
+
 ## Runtime scriptlets
 
 Runtime scriptlets are executed at the time of install and erase of the

macros.in

@@ -1349,7 +1349,6 @@ end
 
 # Global buildsystem defaults
 %buildsystem_default_prep() %autosetup -p1 %*
-%buildsystem_default_clean() %{__rm} -rf %{buildroot}
 
 # \endverbatim
 #*/

tests/rpmbuild.at

@@ -183,7 +183,6 @@ Executing(%conf)
 Executing(%build)
 Executing(%install)
 Executing(%check)
-Executing(%clean)
 Executing(rmbuild)
 ],
 [])
@@ -199,7 +198,6 @@ Executing(%conf)
 Executing(%build)
 Executing(%install)
 Executing(%check)
-Executing(%clean)
 Executing(rmbuild)
 ],
 [])