dashboard/app: support gerrit servers as a webgit source

Gerrit servers return base64 encoded file content.
To get the raw data, &format=TEXT request param is needed.

3 files changed, 29 insertions, 7 deletions

diff --git a/dashboard/app/config.go b/dashboard/app/config.go
index c71d09d8e..836344954 100644
--- a/dashboard/app/config.go
+++ b/dashboard/app/config.go
@@ -165,6 +165,7 @@ type CoverageConfig struct {
 	DashboardClientName string
 
 	// WebGitURI specifies where can we get the kernel file source code directly from AppEngine.
+	// It may be the Git or Gerrit compatible repo.
 	WebGitURI string
 }
 
diff --git a/dashboard/app/coverage.go b/dashboard/app/coverage.go
index 3535dff9e..4c83f299f 100644
--- a/dashboard/app/coverage.go
+++ b/dashboard/app/coverage.go
@@ -146,7 +146,10 @@ func handleHeatmap(c context.Context, w http.ResponseWriter, r *http.Request, f
 
 func makeProxyURIProvider(url string) covermerger.FuncProxyURI {
 	return func(filePath, commit string) string {
-		return fmt.Sprintf("%s/%s/%s", url, commit, filePath)
+		// Parameter format=TEXT is ignored by git servers but is processed by gerrit servers.
+		// Gerrit returns base64 encoded data.
+		// Git return the plain text data.
+		return fmt.Sprintf("%s/%s/%s?format=TEXT", url, commit, filePath)
 	}
 }
 
diff --git a/pkg/covermerger/provider_web.go b/pkg/covermerger/provider_web.go
index e172d47e9..1c0442cae 100644
--- a/pkg/covermerger/provider_web.go
+++ b/pkg/covermerger/provider_web.go
@@ -4,11 +4,13 @@
 package covermerger
 
 import (
+	"encoding/base64"
 	"errors"
 	"fmt"
 	"io"
 	"net/http"
 	"net/url"
+	"strings"
 )
 
 type FuncProxyURI func(filePath, commit string) string
@@ -52,25 +54,41 @@ func (mr *webGit) loadFile(filePath, repo, commit string) ([]byte, error) {
 	}
 	u.Scheme = "https"
 	uri = u.String()
-	res, err := http.Get(uri)
+	resp, err := http.Get(uri)
 	if err != nil {
 		return nil, fmt.Errorf("failed to http.Get: %w", err)
 	}
-	defer res.Body.Close()
+	defer resp.Body.Close()
 
-	if res.StatusCode == 404 {
+	if resp.StatusCode == 404 {
 		return nil, errFileNotFound
 	}
-	if res.StatusCode != 200 {
-		return nil, fmt.Errorf("error: status %d getting '%s'", res.StatusCode, uri)
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("error: status %d getting '%s'", resp.StatusCode, uri)
 	}
-	body, err := io.ReadAll(res.Body)
+	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return nil, fmt.Errorf("failed to io.ReadAll from body: %w", err)
 	}
+	if isGerritServer(resp) {
+		if body, err = base64.StdEncoding.DecodeString(string(body)); err != nil {
+			return nil, fmt.Errorf("base64.StdEncoding.DecodeString: %w", err)
+		}
+	}
 	return body, nil
 }
 
+func isGerritServer(resp *http.Response) bool {
+	for _, headerVals := range resp.Header {
+		for _, header := range headerVals {
+			if strings.Contains(header, "gerrit") {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 func MakeWebGit(funcProxy FuncProxyURI) FileVersProvider {
 	return &webGit{
 		funcProxy: funcProxy,