kbuild: improve version string logic

The LOCALVERSION= string passed to "make" will now always be appended to
the kernel version after CONFIG_LOCALVERSION, if it exists, regardless of
whether CONFIG_LOCALVERSION_AUTO is set or not.  This allows users to
uniquely identify their kernel builds with a string.

If CONFIG_LOCALVERSION_AUTO is enabled, the unique SCM tag reported by
setlocalversion (or .scmversion) is appended to the kernel version, if it
exists.  When CONFIG_LOCALVERSION_AUTO is not enabled, a `+' is appended
to the kernel version to represent that the kernel has been revised since
the last release unless "make LOCALVERSION=" was used to uniquely identify
the build.

The end result is this:

 - when LOCALVERSION= is passed to "make", it is appended to the kernel
   version,

 - when CONFIG_LOCALVERSION_AUTO is enabled, a unique SCM identifier is
   appended if the respository has been revised beyond a tagged commit,
   and

 - when CONFIG_LOCALVERSION_AUTO is disabled, a `+' is appended if the
   repository has been revised beyond a tagged commit and LOCALVERSION=
   was not passed to "make".

Examples:

With CONFIG_LOCALVERSION_AUTO: "make" results in
v2.6.32-rc4-00149-ga3ccf63.  If there are uncommited changes to the
respository, it results in v2.6.32-rc4-00149-ga3ccf63-dirty.  If
"make LOCALVERSION=kbuild" were used, it results in
v2.6.32-rc4-kbuild-00149-ga3ccf63-dirty.

Without CONFIG_LOCALVERSION_AUTO, "make" results in v2.6.32-rc4+
unless the repository is at the Linux v2.6.32-rc4 commit (in which
case the version would be v2.6.32-rc4).  If "make LOCALVERSION=kbuild"
were used, it results in v2.6.32-rc4-kbuild.

Also renames variables such as localver-auto and _localver-auto to more
accurately describe what they represent: localver-extra and
scm-identifier, respectively.

Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

1 files changed, 27 insertions, 16 deletions

diff --git a/Makefile b/Makefile
index f9dc25cd9b2..faa320a67bf 100644
--- a/Makefile
+++ b/Makefile
@@ -910,14 +910,19 @@ endif
 #         $(localver)
 #           localversion*               (files without backups, containing '~')
 #           $(CONFIG_LOCALVERSION)      (from kernel config setting)
-#         $(localver-auto)              (only if CONFIG_LOCALVERSION_AUTO is set)
-#           ./scripts/setlocalversion   (SCM tag, if one exists)
-#           $(LOCALVERSION)             (from make command line if provided)
+#         $(LOCALVERSION)               (from make command line, if provided)
+#         $(localver-extra)
+#           $(scm-identifier)           (unique SCM tag, if one exists)
+#             ./scripts/setlocalversion (only with CONFIG_LOCALVERSION_AUTO)
+#             .scmversion               (only with CONFIG_LOCALVERSION_AUTO)
+#           +                           (only without CONFIG_LOCALVERSION_AUTO
+#                                        and without LOCALVERSION= and
+#                                        repository is at non-tagged commit)
 #
-#  Note how the final $(localver-auto) string is included *only* if the
-# kernel config option CONFIG_LOCALVERSION_AUTO is selected.  Also, at the
-# moment, only git is supported but other SCMs can edit the script
-# scripts/setlocalversion and add the appropriate checks as needed.
+# For kernels without CONFIG_LOCALVERSION_AUTO compiled from an SCM that has
+# been revised beyond a tagged commit, `+' is appended to the version string
+# when not overridden by using "make LOCALVERSION=".  This indicates that the
+# kernel is not a vanilla release version and has been modified.
 
 pattern = ".*/localversion[^~]*"
 string  = $(shell cat /dev/null \
@@ -926,26 +931,32 @@ string  = $(shell cat /dev/null \
 localver = $(subst $(space),, $(string) \
                               $(patsubst "%",%,$(CONFIG_LOCALVERSION)))
 
-# If CONFIG_LOCALVERSION_AUTO is set scripts/setlocalversion is called
-# and if the SCM is know a tag from the SCM is appended.
-# The appended tag is determined by the SCM used.
+# scripts/setlocalversion is called to create a unique identifier if the source
+# is managed by a known SCM and the repository has been revised since the last
+# tagged (release) commit.  The format of the identifier is determined by the
+# SCM's implementation.
 #
 # .scmversion is used when generating rpm packages so we do not loose
 # the version information from the SCM when we do the build of the kernel
 # from the copied source
-ifdef CONFIG_LOCALVERSION_AUTO
-
 ifeq ($(wildcard .scmversion),)
-        _localver-auto = $(shell $(CONFIG_SHELL) \
+        scm-identifier = $(shell $(CONFIG_SHELL) \
                          $(srctree)/scripts/setlocalversion $(srctree))
 else
-        _localver-auto = $(shell cat .scmversion 2> /dev/null)
+        scm-identifier = $(shell cat .scmversion 2> /dev/null)
 endif
 
-        localver-auto  = $(LOCALVERSION)$(_localver-auto)
+ifdef CONFIG_LOCALVERSION_AUTO
+        localver-extra = $(scm-identifier)
+else
+        ifneq ($scm-identifier,)
+                ifeq ($(LOCALVERSION),)
+                        localver-extra = +
+                endif
+        endif
 endif
 
-localver-full = $(localver)$(localver-auto)
+localver-full = $(localver)$(LOCALVERSION)$(localver-extra)
 
 # Store (new) KERNELRELASE string in include/config/kernel.release
 kernelrelease = $(KERNELVERSION)$(localver-full)