Charts: Check for output dir conflicts (#710)

Closes #508

Whenever two charts will end up in the same dir, tanka will exit before doing anything

Ex, these two versions would end up in the flagger dir:
```yaml
directory: charts
repositories:
- name: flagger
  url: https://flagger.app
requires:
- chart: flagger/flagger
  version: 1.16.1
- chart: flagger/flagger
  version: 1.17.0
version: 1
```

```console
$ tk tool charts vendor
Error: Output directory conflicts found:
 - output directory "flagger" is used twice, by charts "flagger/[email protected]" and "flagger/[email protected]"
```

It checks in both `add` and `vendor` commands to handle the case where someone writes their YAML manually

pkg/helm/charts.go

@@ -91,6 +91,11 @@ func (c Charts) Vendor(prune bool) error {
 		return err
 	}
 
+	// Check that there are no output conflicts before vendoring
+	if err := c.Manifest.Requires.CheckForOutputConflicts(); err != nil {
+		return err
+	}
+
 	expectedDirs := make(map[string]bool)
 
 	repositoriesUpdated := false
@@ -176,25 +181,30 @@ func (c *Charts) Add(reqs []string) error {
 	log.Printf("Adding %v Charts ...", len(reqs))
 
 	// parse new charts, append in memory
-	added := 0
+	requirements := c.Manifest.Requires
 	for _, s := range reqs {
 		r, err := parseReq(s)
 		if err != nil {
 			skip(s, err)
 			continue
 		}
 
-		if c.Manifest.Requires.Has(*r) {
+		if requirements.Has(*r) {
 			skip(s, fmt.Errorf("already exists"))
 			continue
 		}
 
-		c.Manifest.Requires = append(c.Manifest.Requires, *r)
-		added++
+		requirements = append(requirements, *r)
 		log.Println(" OK:", s)
 	}
 
+	if err := requirements.CheckForOutputConflicts(); err != nil {
+		return err
+	}
+
 	// write out
+	added := len(requirements) - len(c.Manifest.Requires)
+	c.Manifest.Requires = requirements
 	if err := write(c.Manifest, c.ManifestFile()); err != nil {
 		return err
 	}

pkg/helm/charts_test.go

@@ -38,6 +38,11 @@ func TestAdd(t *testing.T) {
 	err = c.Add([]string{"stable/[email protected]"})
 	assert.EqualError(t, err, "1 Chart(s) were skipped. Please check above logs for details")
 
+	// Adding a chart with a different version to the same path, causes a conflict
+	err = c.Add([]string{"stable/[email protected]"})
+	assert.EqualError(t, err, `Output directory conflicts found:
+ - output directory "prometheus" is used twice, by charts "stable/[email protected]" and "stable/[email protected]"`)
+
 	// Add a chart with a specific extract directory
 	err = c.Add([]string{"stable/[email protected]:prometheus-11.12.0"})
 	assert.NoError(t, err)

pkg/helm/spec.go

@@ -2,6 +2,7 @@ package helm
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/Masterminds/semver"
 )
@@ -87,3 +88,25 @@ func (r Requirements) Has(req Requirement) bool {
 
 	return false
 }
+
+func (r Requirements) CheckForOutputConflicts() error {
+	outputDirs := make(map[string]Requirement)
+	errs := make([]string, 0)
+
+	for _, req := range r {
+		dir := req.Directory
+		if dir == "" {
+			dir = parseReqName(req.Chart)
+		}
+		if previous, ok := outputDirs[dir]; ok {
+			errs = append(errs, fmt.Sprintf(`output directory %q is used twice, by charts "%s@%s" and "%s@%s"`, dir, previous.Chart, previous.Version.String(), req.Chart, req.Version.String()))
+		}
+		outputDirs[dir] = req
+	}
+
+	if len(errs) > 0 {
+		return fmt.Errorf("Output directory conflicts found:\n - " + strings.Join(errs, "\n - "))
+	}
+
+	return nil
+}