buildhistory: Allow customising buildhistory tags

Allow setting custom buildhistory tag prefixes. This allows multiple
build directories to share one buildhistory git repository with multiple
worktrees.

(From OE-Core rev: 1bb2aa53a74e36dc3ba901b9d8ce780e7880cef8)

Signed-off-by: Daniel McGregor <daniel.mcgregor@vecima.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/buildhistory.bbclass

@@ -40,6 +40,7 @@ BUILDHISTORY_SDK_FILES ?= "conf/local.conf conf/bblayers.conf conf/auto.conf con
 BUILDHISTORY_COMMIT ?= "1"
 BUILDHISTORY_COMMIT_AUTHOR ?= "buildhistory <buildhistory@${DISTRO}>"
 BUILDHISTORY_PUSH_REPO ?= ""
+BUILDHISTORY_TAG ?= "build"
 
 SSTATEPOSTINSTFUNCS_append = " buildhistory_emit_pkghistory"
 # We want to avoid influencing the signatures of sstate tasks - first the function itself:
@@ -824,9 +825,9 @@ END
 		if [ ! -e .git ] ; then
 			git init -q
 		else
-			git tag -f build-minus-3 build-minus-2 > /dev/null 2>&1 || true
-			git tag -f build-minus-2 build-minus-1 > /dev/null 2>&1 || true
-			git tag -f build-minus-1 > /dev/null 2>&1 || true
+			git tag -f ${BUILDHISTORY_TAG}-minus-3 ${BUILDHISTORY_TAG}-minus-2 > /dev/null 2>&1 || true
+			git tag -f ${BUILDHISTORY_TAG}-minus-2 ${BUILDHISTORY_TAG}-minus-1 > /dev/null 2>&1 || true
+			git tag -f ${BUILDHISTORY_TAG}-minus-1 > /dev/null 2>&1 || true
 		fi
 
 		check_git_config