From c14183adcabd020b72c29f224f94bd90f9cead12 Mon Sep 17 00:00:00 2001
From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Fri, 22 Mar 2013 11:27:20 -0700
Subject: [PATCH] Use 'git describe' for working builds

When building from an arbitrary commit in the git tree it's useful
for the resulting packages to be uniquely identifiable.  Therefore,
the build system has been updated to detect if your compiling in
git tree.

If you are building in a git tree, and there are commits after the
last annotated tag.  Then the <id>-<hash> component of 'git describe'
will be used to overwrite the 'Release:' field in the META file.

The only tricky part is that to ensure the 'make dist' tarball is
built using the correct release.  A dist-hook was added to the top
level make file to rewrite the META file using the correct release.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #195
Issue #111
---
 Makefile.am        |  4 ++++
 config/spl-meta.m4 | 22 ++++++++++++++++++----
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/Makefile.am b/Makefile.am
index 232c305239d1..cea9db97b153 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -32,6 +32,10 @@ distclean-local::
 		-o -name '*.order' -o -name '*.markers' \) \
 		-type f -print | xargs $(RM)
 
+dist-hook:
+	sed -i 's/Release:[[:print:]]*/Release:      $(RELEASE)/' \
+		$(distdir)/META
+
 ctags:
 	$(RM) $(top_srcdir)/tags
 	find $(top_srcdir) -name .git -prune -o -name '*.[hc]' | xargs ctags
diff --git a/config/spl-meta.m4 b/config/spl-meta.m4
index af8be801a94e..28103bc103aa 100644
--- a/config/spl-meta.m4
+++ b/config/spl-meta.m4
@@ -2,16 +2,20 @@
 # Written by Chris Dunlap <cdunlap@llnl.gov>.
 # Modified by Brian Behlendorf <behlendorf1@llnl.gov>.
 ###############################################################################
-# SPL_AC_META: Read metadata from the META file.
+# SPL_AC_META: Read metadata from the META file.  When building from a
+# git repository the SPL_META_RELEASE field will be overwritten if there
+# is an annotated tag matching the form SPL_META_NAME-SPL_META_VERSION-*.
+# This allows for working builds to be uniquely identified using the git
+# commit hash.
 ###############################################################################
 
 AC_DEFUN([SPL_AC_META], [
 	AC_MSG_CHECKING([metadata])
 
 	META="$srcdir/META"
-	_spl_ac_meta_got_file=no
+	_spl_ac_meta_type="none"
 	if test -f "$META"; then
-		_spl_ac_meta_got_file=yes
+		_spl_ac_meta_type="META file"
 
 		SPL_META_NAME=_SPL_AC_META_GETVAL([(?:NAME|PROJECT|PACKAGE)]);
 		if test -n "$SPL_META_NAME"; then
@@ -30,6 +34,16 @@ AC_DEFUN([SPL_AC_META], [
 		fi
 
 		SPL_META_RELEASE=_SPL_AC_META_GETVAL([RELEASE]);
+		if git rev-parse --git-dir > /dev/null 2>&1; then
+			_match="${SPL_META_NAME}-${SPL_META_VERSION}*"
+			_alias=$(git describe --match=${_match} 2>/dev/null)
+			_release=$(echo ${_alias}|cut -f3- -d'-'|sed 's/-/_/g')
+			if test -n "${_release}"; then
+				SPL_META_RELEASE=${_release}
+				_spl_ac_meta_type="git describe"
+			fi
+		fi
+
 		if test -n "$SPL_META_RELEASE"; then
 			AC_DEFINE_UNQUOTED([SPL_META_RELEASE], ["$SPL_META_RELEASE"],
 				[Define the project release.]
@@ -97,7 +111,7 @@ AC_DEFUN([SPL_AC_META], [
 		fi
 	fi
 
-	AC_MSG_RESULT([$_spl_ac_meta_got_file])
+	AC_MSG_RESULT([$_spl_ac_meta_type])
 	]
 )