Add optional switch for disabling custom git fetch

CHANGELOG.md

@@ -30,6 +30,7 @@ All notable changes to Sourcegraph are documented in this file.
 - All Perforce rules are now stored together in one column and evaluated on a "last rule takes precedence" basis. [#41785](https://github.com/sourcegraph/sourcegraph/pull/41785)
 - Security events are now a part of the audit log. [#42653](https://github.com/sourcegraph/sourcegraph/pull/42653)
 - "GC AUTO" is now the default garbage collection job. We disable sg maintenance, which had previously replace "GC AUTO", after repeated reports about repo corruption. [#42856](https://github.com/sourcegraph/sourcegraph/pull/42856) 
+- To use the optional `customGitFetch` feature, the `ENABLE_CUSTOM_GIT_FETCH` env var must be set on `gitserver`. [#42704](https://github.com/sourcegraph/sourcegraph/pull/42704)
 
 ### Fixed
 

cmd/gitserver/server/customfetch.go

@@ -6,7 +6,9 @@ import (
 	"path"
 	"strings"
 
+	"github.com/sourcegraph/log"
 	"github.com/sourcegraph/sourcegraph/internal/conf"
+	"github.com/sourcegraph/sourcegraph/internal/env"
 	"github.com/sourcegraph/sourcegraph/internal/vcs"
 	"github.com/sourcegraph/sourcegraph/schema"
 )
@@ -16,8 +18,17 @@ var customGitFetch = conf.Cached(func() map[string][]string {
 	return buildCustomFetchMappings(exp.CustomGitFetch)
 })
 
+var enableCustomGitFetch = env.Get("ENABLE_CUSTOM_GIT_FETCH", "false", "Enable custom git fetch")
+
 func buildCustomFetchMappings(c []*schema.CustomGitFetchMapping) map[string][]string {
-	if c == nil {
+	// this is an edge case where a CustomGitFetchMapping has been made but enableCustomGitFetch is false
+	if c != nil && enableCustomGitFetch == "false" {
+		logger := log.Scoped("customfetch", "")
+		logger.Warn("a CustomGitFetchMapping is configured but ENABLE_CUSTOM_GIT_FETCH is not set")
+
+		return map[string][]string{}
+	}
+	if c == nil || enableCustomGitFetch == "false" {
 		return map[string][]string{}
 	}
 

cmd/gitserver/server/customfetch_test.go

@@ -22,6 +22,26 @@ func TestEmptyCustomGitFetch(t *testing.T) {
 	}
 }
 
+func TestDisabledCustomGitFetch(t *testing.T) {
+	mapping := []*schema.CustomGitFetchMapping{
+		{
+			DomainPath: "github.com/foo/normal/one",
+			Fetch:      "echo normal one",
+		},
+	}
+	remoteUrl := "https://8cd1419f4d5c1e0527f2893c9422f1a2a435116d@github.com/foo/normal/one"
+
+	customGitFetch = func() map[string][]string {
+		return buildCustomFetchMappings(mapping)
+	}
+
+	remoteURL, _ := vcs.ParseURL(remoteUrl)
+	customCmd := customFetchCmd(context.Background(), remoteURL)
+	if customCmd != nil {
+		t.Errorf("expected nil custom cmd for empty configuration, got %+v", customCmd)
+	}
+}
+
 func TestCustomGitFetch(t *testing.T) {
 	mappings := []*schema.CustomGitFetchMapping{
 		{
@@ -66,6 +86,11 @@ func TestCustomGitFetch(t *testing.T) {
 		},
 	}
 
+	// env var ENABLE_CUSTOM_GIT_FETCH is set to true
+	enableCustomGitFetch = "true"
+	t.Cleanup(func() {
+		enableCustomGitFetch = "false"
+	})
 	customGitFetch = func() map[string][]string {
 		return buildCustomFetchMappings(mappings)
 	}

schema/site.schema.json

@@ -303,7 +303,7 @@
           }
         },
         "customGitFetch": {
-          "description": "JSON array of configuration that maps from Git clone URL domain/path to custom git fetch command.",
+          "description": "JSON array of configuration that maps from Git clone URL domain/path to custom git fetch command. To enable this feature set environment variable `ENABLE_CUSTOM_GIT_FETCH` as `true` on gitserver.",
           "type": "array",
           "items": {
             "title": "CustomGitFetchMapping",