If can't find hrev tags set the version to the short hash

If no hrev tags are found the revision is blank and shows up as
0 in About System. This commit updates the revision function so that
it falls back to the current short hash instead. Only affects devel
builds and only if you've deleted your tags.

build/scripts/determine_haiku_revision

@@ -8,7 +8,7 @@ determineGitRevision()
 	revision=`cat ${haikuBuildOutputDir}/haiku-revision 2>/dev/null`
 	lastBuiltRevision=`cat ${haikuBuildOutputDir}/last-built-revision \
 		2>/dev/null`
-	localRev=`git rev-list -n1 HEAD`
+	localRev=`git rev-parse HEAD`
 
 	# only determine the haiku-revision if anything has changed from
 	# last build
@@ -16,7 +16,10 @@ determineGitRevision()
 		# the revision we use is the description of HEAD with respect to the
 		# last reachable hrev-(haiku-revision-)tag
 		revision=`git describe --dirty --tags --match=hrev*`
-		if echo "$revision" | grep -- '-' >/dev/null; then
+		if [ -z "$revision" ]; then
+			# failed to find any hrev tags, use short hash instead
+			revision=`git rev-parse --short HEAD`
+		elif echo "$revision" | grep -- '-' >/dev/null; then
 			# HEAD is not directly a changeset from Haiku's central repo, so we
 			# add the current branch name as additional info
 			branchName=`git branch | grep '*' | cut -b 3-`
@@ -59,7 +62,7 @@ determineHaikuRevision()
 			grep --max-count=1 "(svn r" |
 			$SED -n -e 's,(svn r\(.*\)).*,\1,p'`
 	fi
-	if [ "$revision" = "" ]; then
+	if [ -z "$revision" ]; then
 		revision=0
 	fi
 	echo $revision >${haikuBuildOutputDir}/haiku-revision