Add since flag for changing the reference branch for git merge-base (#229)

pkg/chart/chart.go

@@ -675,7 +675,7 @@ func (t *Testing) computeMergeBase() (string, error) {
 	if err != nil {
 		return "", errors.New("Must be in a git repository")
 	}
-	return t.git.MergeBase(fmt.Sprintf("%s/%s", t.config.Remote, t.config.TargetBranch), "HEAD")
+	return t.git.MergeBase(fmt.Sprintf("%s/%s", t.config.Remote, t.config.TargetBranch), t.config.Since)
 }
 
 // ComputeChangedChartDirectories takes the merge base of HEAD and the configured remote and target branch and computes a

pkg/config/config.go

@@ -41,6 +41,7 @@ var (
 type Configuration struct {
 	Remote                string   `mapstructure:"remote"`
 	TargetBranch          string   `mapstructure:"target-branch"`
+	Since                 string   `mapstructure:"since"`
 	BuildId               string   `mapstructure:"build-id"`
 	LintConf              string   `mapstructure:"lint-conf"`
 	ChartYamlSchema       string   `mapstructure:"chart-yaml-schema"`

pkg/config/test_config.json

@@ -1,6 +1,7 @@
 {
     "remote": "origin",
     "target-branch": "master",
+    "since": "HEAD~1",
     "build-id": "pr-42",
     "lint-conf": "my-lint-conf.yaml",
     "chart-yaml-schema": "my-chart-yaml-schema.yaml",

pkg/config/test_config.yaml

@@ -1,5 +1,6 @@
 remote: origin
 target-branch: master
+since: HEAD~1
 build-id: pr-42
 lint-conf: my-lint-conf.yaml
 chart-yaml-schema: my-chart-yaml-schema.yaml