docs: image base reference

Fixes #247

this makes an ephemeral header that gets included into the html doc that
bases the images path to pull from the same tag on github.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

.gitignore

@@ -1,2 +1,3 @@
 /oci-validate-examples
 output
+header.html

.tool/genheader.go

@@ -0,0 +1,42 @@
+// Copyright 2017 The Linux Foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"os"
+	"strings"
+	"text/template"
+
+	specs "github.com/opencontainers/image-spec/specs-go"
+)
+
+var headerTemplate = template.Must(template.New("gen").Parse(`<title>image-spec {{.Version}}</title>
+<base href="https://raw.githubusercontent.com/opencontainers/image-spec/{{.Branch}}/">`))
+
+type Obj struct {
+	Version string
+	Branch  string
+}
+
+func main() {
+	obj := Obj{
+		Version: specs.Version,
+		Branch:  specs.Version,
+	}
+	if strings.HasSuffix(specs.Version, "-dev") {
+		obj.Branch = "master"
+	}
+	headerTemplate.Execute(os.Stdout, obj)
+}

Makefile

@@ -68,13 +68,16 @@ $(OUTPUT_DIRNAME)/$(DOC_FILENAME).pdf: $(DOC_FILES) $(FIGURE_FILES)
 	$(PANDOC) -f markdown_github -t latex -o $(PANDOC_DST)$@ $(patsubst %,$(PANDOC_SRC)%,$(DOC_FILES))
 	ls -sh $(shell readlink -f $@)
 
-$(OUTPUT_DIRNAME)/$(DOC_FILENAME).html: $(DOC_FILES) $(FIGURE_FILES)
+$(OUTPUT_DIRNAME)/$(DOC_FILENAME).html: header.html $(DOC_FILES) $(FIGURE_FILES)
 	@mkdir -p $(OUTPUT_DIRNAME)/ && \
 	cp -ap img/ $(shell pwd)/$(OUTPUT_DIRNAME)/&& \
-	$(PANDOC) -f markdown_github -t html5 -o $(PANDOC_DST)$@ $(patsubst %,$(PANDOC_SRC)%,$(DOC_FILES))
+	$(PANDOC) -f markdown_github -t html5 -H $(PANDOC_SRC)/header.html --standalone -o $(PANDOC_DST)$@ $(patsubst %,$(PANDOC_SRC)%,$(DOC_FILES))
 	ls -sh $(shell readlink -f $@)
 endif
 
+header.html: .tool/genheader.go specs-go/version.go
+	go run .tool/genheader.go > $@
+
 validate-examples:
 	go test -run TestValidate ./schema
 
@@ -121,7 +124,7 @@ install.tools: .install.gitvalidation .install.glide .install.glide-vc
 	go get -u github.com/sgotti/glide-vc
 
 clean:
-	rm -rf *~ $(OUTPUT_DIRNAME)
+	rm -rf *~ $(OUTPUT_DIRNAME) header.html
 
 .PHONY: \
 	validate-examples \