add hotfix+commit-id+docker builds

Makefile

@@ -71,10 +71,15 @@ build: checks
 	@echo "Building minio binary to './minio'"
 	@GO111MODULE=on CGO_ENABLED=0 go build -tags kqueue -trimpath --ldflags "$(LDFLAGS)" -o $(PWD)/minio 1>/dev/null
 
-hotfix: LDFLAGS := $(shell MINIO_RELEASE="RELEASE" MINIO_HOTFIX="hotfix" go run buildscripts/gen-ldflags.go $(shell git describe --tags --abbrev=0 | \
+hotfix: LDFLAGS := $(shell MINIO_RELEASE="RELEASE" MINIO_HOTFIX="hotfix.$(shell git rev-parse --short HEAD)" go run buildscripts/gen-ldflags.go $(shell git describe --tags --abbrev=0 | \
     sed 's#RELEASE\.\([0-9]\+\)-\([0-9]\+\)-\([0-9]\+\)T\([0-9]\+\)-\([0-9]\+\)-\([0-9]\+\)Z#\1-\2-\3T\4:\5:\6Z#'))
+	TAG := "minio/minio:$(shell git describe --tags --abbrev=0).hotfix.$(shell git rev-parse --short HEAD)"
 hotfix: install
 
+docker-hotfix: hotfix checks
+	@echo "Building minio docker image '$(TAG)'"
+	@docker build -t $(TAG) . -f Dockerfile.dev
+
 docker: checks
 	@echo "Building minio docker image '$(TAG)'"
 	@GOOS=linux GO111MODULE=on CGO_ENABLED=0 go build -tags kqueue -trimpath --ldflags "$(LDFLAGS)" -o $(PWD)/minio 1>/dev/null