From bdd7e7163b8661d05748e431186185f3373841d3 Mon Sep 17 00:00:00 2001
From: Ian Campbell <ian.campbell@docker.com>
Date: Wed, 28 Jun 2017 12:43:36 +0100
Subject: [PATCH] pkg: Allow override of commit to calculate hash for show-tag

Useful to answer the question of what the hash was at the point of some older
commit.

$ make --no-print-directory -C pkg/init/ show-tag
linuxkit/init:36c56f0664d49c5a6adc1120d1bf5ba6ac30b389
$ make --no-print-directory -C pkg/init/ show-tag HASH_COMMIT=4699f80ef73141ee87a77d03f93065e541fab382
linuxkit/init:17693d233dd009b2a3a8d23673cb85969e1dce80

Signed-off-by: Ian Campbell <ian.campbell@docker.com>
---
 pkg/package.mk | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/pkg/package.mk b/pkg/package.mk
index 6f32c4eb1..5ca8c14c1 100644
--- a/pkg/package.mk
+++ b/pkg/package.mk
@@ -2,10 +2,13 @@
 default: push
 
 ORG?=linuxkit
-HASH?=$(shell git ls-tree --full-tree HEAD -- $(CURDIR) | awk '{print $$3}')
+HASH_COMMIT?=HEAD # Setting this is only really useful with the show-tag target
+HASH?=$(shell git ls-tree --full-tree $(HASH_COMMIT) -- $(CURDIR) | awk '{print $$3}')
 BASE_DEPS=Dockerfile Makefile
 
+ifneq ($(HASH_COMMIT),HEAD) # Others can't be dirty by definition
 DIRTY=$(shell git diff-index --quiet HEAD -- $(CURDIR) || echo "-dirty")
+endif
 TAG=$(ORG)/$(IMAGE):$(HASH)$(DIRTY)
 
 # Get a release tag, if present