fix: the concurrency issue with git detached processing in Repo Server (argoproj#25101) (argoproj#25127)

Signed-off-by: Eugene Doudine <eugene.doudine@octopus.com>

Author: dudinea

cmd/argocd-repo-server/commands/argocd_repo_server.go

@@ -80,6 +80,7 @@ func NewCommand() *cobra.Command {
 		includeHiddenDirectories           bool
 		cmpUseManifestGeneratePaths        bool
 		ociMediaTypes                      []string
+		enableBuiltinGitConfig             bool
 	)
 	command := cobra.Command{
 		Use:               cliName,
@@ -155,6 +156,7 @@ func NewCommand() *cobra.Command {
 				IncludeHiddenDirectories:                     includeHiddenDirectories,
 				CMPUseManifestGeneratePaths:                  cmpUseManifestGeneratePaths,
 				OCIMediaTypes:                                ociMediaTypes,
+				EnableBuiltinGitConfig:                       enableBuiltinGitConfig,
 			}, askPassServer)
 			errors.CheckError(err)
 
@@ -265,6 +267,7 @@ func NewCommand() *cobra.Command {
 	command.Flags().BoolVar(&includeHiddenDirectories, "include-hidden-directories", env.ParseBoolFromEnv("ARGOCD_REPO_SERVER_INCLUDE_HIDDEN_DIRECTORIES", false), "Include hidden directories from Git")
 	command.Flags().BoolVar(&cmpUseManifestGeneratePaths, "plugin-use-manifest-generate-paths", env.ParseBoolFromEnv("ARGOCD_REPO_SERVER_PLUGIN_USE_MANIFEST_GENERATE_PATHS", false), "Pass the resources described in argocd.argoproj.io/manifest-generate-paths value to the cmpserver to generate the application manifests.")
 	command.Flags().StringSliceVar(&ociMediaTypes, "oci-layer-media-types", env.StringsFromEnv("ARGOCD_REPO_SERVER_OCI_LAYER_MEDIA_TYPES", []string{"application/vnd.oci.image.layer.v1.tar", "application/vnd.oci.image.layer.v1.tar+gzip", "application/vnd.cncf.helm.chart.content.v1.tar+gzip"}, ","), "Comma separated list of allowed media types for OCI media types. This only accounts for media types within layers.")
+	command.Flags().BoolVar(&enableBuiltinGitConfig, "enable-builtin-git-config", env.ParseBoolFromEnv("ARGOCD_REPO_SERVER_ENABLE_BUILTIN_GIT_CONFIG", true), "Enable builtin git configuration options that are required for correct argocd-repo-server operation.")
 	tlsConfigCustomizerSrc = tls.AddTLSFlagsToCmd(&command)
 	cacheSrc = reposervercache.AddCacheFlagsToCmd(&command, cacheutil.Options{
 		OnClientCreated: func(client *redis.Client) {

docs/operator-manual/argocd-cmd-params-cm.yaml

@@ -219,6 +219,8 @@ data:
   reposerver.git.lsremote.parallelism.limit: "0"
   # Git requests timeout.
   reposerver.git.request.timeout: "15s"
+  # Enable builtin git configuration options that are required for correct argocd-repo-server operation (default "true")
+  reposerver.enable.builtin.git.config: "true"
   # Include hidden directories from Git
   reposerver.include.hidden.directories: "false"
 

docs/operator-manual/git_configuration.md

@@ -0,0 +1,43 @@
+
+# Git Configuration
+
+## System Configuration
+
+Argo CD uses the Git installation from its base image (Ubuntu), which
+includes a standard system configuration file located at
+`/etc/gitconfig`. This file is minimal, just defining filters
+necessary for Git LFS functionality.
+
+You can customize Git's system configuration by mounting a file from a
+ConfigMap or by creating a custom Argo CD image.
+
+## Global Configuration
+
+Argo CD runs Git with the `HOME` environment variable set to
+`/dev/null`. As a result, global Git configuration is not supported.
+
+## Built-in Configuration
+
+The `argocd-repo-server` adds specific configuration parameters to the
+Git environment to ensure proper Argo CD operation. These built-in
+settings override any conflicting values from the system Git
+configuration.
+
+Currently, the following built-in configuration options are set:
+
+- `maintenance.autoDetach=false`
+- `gc.autoDetach=false`
+
+These settings force Git's repository maintenance tasks to run in the
+foreground. This prevents Git from running detached background
+processes that could modify the repository and interfere with
+subsequent Git invocations from `argocd-repo-server`.
+
+You can disable these built-in settings by setting the
+`argocd-cmd-params-cm` value `reposerver.enable.builtin.git.config` to
+`"false"`. This allows you to experiment with background processing or
+if you are certain that concurrency issues will not occur in your
+environment.
+
+> [!NOTE]
+> Disabling this is not recommended and is not supported!

docs/operator-manual/server-commands/argocd-repo-server.md

@@ -239,6 +239,12 @@ spec:
                 key: reposerver.git.request.timeout
                 name: argocd-cmd-params-cm
                 optional: true
+          - name: ARGOCD_REPO_SERVER_ENABLE_BUILTIN_GIT_CONFIG
+            valueFrom:
+              configMapKeyRef:
+                name: argocd-cmd-params-cm
+                key: reposerver.enable.builtin.git.config
+                optional: true
           - name: ARGOCD_GRPC_MAX_SIZE_MB
             valueFrom:
               configMapKeyRef: