--- a/doc/makefile-variables.txt	Thu Sep 08 17:47:13 2016 -0700
+++ b/doc/makefile-variables.txt	Thu Sep 15 11:53:59 2016 -0700
@@ -2,22 +2,43 @@
 Makefiles.  To distinguish these from the Makefile(s) that are part of each
 component distribution, the latter will be referred to as native Makefiles.
 
-The following are the basics that just about every Makefile should have.
+The following are the basics that just about every Makefile should have.  Most
+have defaults, but can be overridden.
+
+* BUILD_ARCH declares which architecture this component should be built for;
+  possible values are: i386, sparc.  If not set, the component will be built
+  for both.
 
 * BUILD_BITS declares which bits this component should be built for and
   which binaries are the preferred ones (i.e. should be installed in /usr/bin);
-  values are: 64, 64_and_32, 32, 32_and_64.
+  values are: 64, 64_and_32, 32, 32_and_64, and NO_ARCH.
+
 * COMPONENT_NAME is typically a short name (e.g., vim).
+
 * COMPONENT_VERSION is typically numbers separated by dots (e.g. 7.3).
+
 * COMPONENT_SRC is where the archive is extracted; it has a default value of
   "$(COMPONENT_NAME)-$(COMPONENT_VERSION)".
+
 * COMPONENT_PROJECT_URL is the general web site for the component.
+
 * COMPONENT_ARCHIVE is the base name of the archive to be downloaded; it has
   a default value of "$(COMPONENT_SRC).tar.gz".
+
 * COMPONENT_ARCHIVE_HASH is typically "sha256:" followed by the first output
   field of `sha256sum $(COMPONENT_ARCHIVE)`.
+
+* COMPONENT_ARCHIVE_SRC defines what kind of object delivers the source.  This
+  can be "git", "hg", or "svn" if the source comes from an SCM repository, and
+  must be "none" if the source is checked into the Userland repository
+  directly.
+
 * COMPONENT_ARCHIVE_URL is where the archive can be downloaded from.  This is
   typically constructed from $(COMPONENT_PROJECT_URL) and $(COMPONENT_ARCHIVE).
+
+* COMPONENT_BUGDB is the lower-case rendering of the BugDB cat/subcat; it has
+  a default value of "utility/$(COMPONENT_NAME)".
+
 * COMPONENT_SIG_URL is the URL where the PGP signature for $(COMPONENT_ARCHIVE)
   can be found.  This can be used in addition to the hash in
   $(COMPONENT_ARCHIVE_HASH) to verify the correctness of the archive.  If
@@ -32,6 +53,11 @@
 	done
   before you 'hg commit' your merge.
 
+* COMPONENT_LABEL is an arbitrary string that will be used as part of
+  COMPONENT_SRC when building an archive from an SCM source repository.  It
+  defaults to COMPONENT_VERSION.  It may be set to empty if desired.  See
+  the relevant makefiles for the full composition.
+
 * GIT_REPO can be used in place of COMPONENT_ARCHIVE_URL to pull the component
   source from the GIT repository referenced in the value.
 * GIT_REV is the tag or changeset that you wish to pull from GIT.
@@ -44,33 +70,9 @@
   source from the Subversion repository referenced in the value.
 * SVN_REV is the tag or changeset that you wish to pull from Subversion.
 
-The following are basic variables that can be overridden but provide default
-values:
-
-* BUILD_ARCH declares which architecture this component should be built for;
-  possible values are: i386, sparc.  If not set, the component will be built
-  for both.
-* COMPONENT_SRC is where the archive is extracted; it has a default value of
-  "$(COMPONENT_NAME)-$(COMPONENT_VERSION)".
-* COMPONENT_ARCHIVE is the base name of the archive to be downloaded; it has
-  a default value of "$(COMPONENT_SRC).tar.gz".
-* COMPONENT_BUGDB is the lower-case rendering of the BugDB cat/subcat; it has
-  a default value of "utility/$(COMPONENT_NAME)".
 * REQUIRED_PACKAGES is a list of packages required to build or run the
   component and its tests; it includes "system/library" by default.
 
-* GIT_REPO can be used in place of COMPONENT_ARCHIVE_URL to pull the component
-  source from the GIT repository referenced in the value.
-* GIT_REV is the tag or changeset that you wish to pull from GIT.
-
-* HG_REPO can be used in place of COMPONENT_ARCHIVE_URL to pull the component
-  source from the Mercurial repository referenced in the value.
-* HG_REV is the tag or changeset that you wish to pull from Mercurial.
-
-* SVN_REPO can be used in place of COMPONENT_ARCHIVE_URL to pull the component
-  source from the Subversion repository referenced in the value.
-* SVN_REV is the tag or changeset that you wish to pull from Subversion.
-
 The following are basic variables that must be set before including common.mk
 if overriding the default: