fix git hook env contamination (#65)

* fix git hook env contamination

* add ts docs

* minor change

---------

Co-authored-by: Pushgate Hook Harness <hook-harness@example.test>

Author: dbrosio3

bin/pushgate.mjs

@@ -1,3 +1,4 @@
+import { sanitizeGitLocalEnv } from "../../git/environment.js";
 import { runCommand } from "../../process/run-command.js";
 import { generateAiReviewOutputJsonSchema } from "../review-contract.js";
 import { createCommandProviderAdapter } from "./command-provider-adapter.js";
@@ -320,7 +321,7 @@ async function isClaudeUnauthenticated(
       args: ["auth", "status"],
       command: "claude",
       cwd: repoRoot,
-      env,
+      env: sanitizeGitLocalEnv(env),
     });
 
     return result.code === 1;

src/ai/providers/claude.ts

@@ -1,3 +1,4 @@
+import { sanitizeGitLocalEnv } from "../../git/environment.js";
 import {
   isProcessCompletionOutcome,
   runProcessOutcome,
@@ -37,7 +38,7 @@ export async function runProviderCommand(options: {
     args: options.args,
     command: options.command,
     cwd: options.cwd,
-    env: options.env,
+    env: sanitizeGitLocalEnv(options.env),
     outputCaptureLimit: options.outputCaptureLimit ?? null,
     outputTailLimit: options.outputTailLimit ?? DEFAULT_OUTPUT_TAIL_LIMIT,
     // Provider CLIs may exit before stdin fully drains; the process runner still

src/ai/providers/run-provider-command.ts

@@ -3,6 +3,7 @@ import {
   type CommandResult,
   type RunCommandOptions,
 } from "../process/run-command.js";
+import { sanitizeGitLocalEnv } from "./environment.js";
 
 export type GitCommandEncoding = "buffer" | "utf8";
 export type GitCommandResult<Stdout extends Buffer | string = string> =
@@ -15,6 +16,7 @@ type GitCommandFailureResult = Pick<
 export interface GitCommandOptions {
   encoding?: GitCommandEncoding;
   env?: NodeJS.ProcessEnv;
+  preserveGitConfigOverlay?: boolean;
 }
 
 export class GitCommandError extends Error {
@@ -51,7 +53,9 @@ export function runGit(
     args,
     command: "git",
     cwd: repoRoot,
-    env: options.env,
+    env: sanitizeGitLocalEnv(options.env ?? process.env, {
+      preserveGitConfigOverlay: options.preserveGitConfigOverlay,
+    }),
   };
 
   if (options.encoding === "buffer") {

src/git/command.ts

@@ -11,12 +11,16 @@ export async function readGitBooleanConfig(
   repoRoot: string,
   key: string,
   env: NodeJS.ProcessEnv = process.env,
+  options: {
+    preserveGitConfigOverlay?: boolean;
+  } = {},
 ): Promise<boolean> {
   let result: Awaited<ReturnType<typeof runGit>>;
 
   try {
     result = await runGit(repoRoot, ["config", "--bool", "--get", key], {
       env,
+      preserveGitConfigOverlay: options.preserveGitConfigOverlay,
     });
   } catch (error) {
     throw new GitConfigError(

src/git/config.ts

@@ -0,0 +1,78 @@
+const GIT_LOCAL_ENV_VARS = new Set([
+  "GIT_ALTERNATE_OBJECT_DIRECTORIES",
+  "GIT_COMMON_DIR",
+  "GIT_CONFIG",
+  "GIT_CONFIG_COUNT",
+  "GIT_CONFIG_PARAMETERS",
+  "GIT_DIR",
+  "GIT_GRAFT_FILE",
+  "GIT_IMPLICIT_WORK_TREE",
+  "GIT_INDEX_FILE",
+  "GIT_NO_REPLACE_OBJECTS",
+  "GIT_OBJECT_DIRECTORY",
+  "GIT_PREFIX",
+  "GIT_REPLACE_REF_BASE",
+  "GIT_SHALLOW_FILE",
+  "GIT_WORK_TREE",
+]);
+
+const GIT_CONFIG_PAIR_ENV_VAR = /^GIT_CONFIG_(?:KEY|VALUE)_\d+$/;
+
+export interface SanitizeGitLocalEnvOptions {
+  /**
+   * Keep `git -c` config passed through Git's environment protocol.
+   * Use only when intentionally reading caller-supplied Git config overlays.
+   */
+  preserveGitConfigOverlay?: boolean;
+}
+
+/**
+ * Removes Git hook-local repository bindings from an environment copy.
+ *
+ * Git hooks can run with `GIT_DIR`, `GIT_WORK_TREE`, `GIT_INDEX_FILE`, and
+ * related variables pointing at the repository being pushed. If Pushgate passes
+ * those variables into tools, plugins, providers, or explicit-`cwd` Git helpers,
+ * nested Git commands may operate on the hook repo instead of their own cwd.
+ */
+export function sanitizeGitLocalEnv(
+  env: NodeJS.ProcessEnv,
+  options: SanitizeGitLocalEnvOptions = {},
+): NodeJS.ProcessEnv {
+  const sanitized: NodeJS.ProcessEnv = {};
+
+  for (const [key, value] of Object.entries(env)) {
+    if (shouldRemoveGitEnvVar(key, options)) {
+      continue;
+    }
+
+    if (value !== undefined) {
+      sanitized[key] = value;
+    }
+  }
+
+  return sanitized;
+}
+
+/** Returns `true` for repository-local Git environment variables. */
+export function isGitLocalEnvVar(key: string): boolean {
+  return GIT_LOCAL_ENV_VARS.has(key) || GIT_CONFIG_PAIR_ENV_VAR.test(key);
+}
+
+function shouldRemoveGitEnvVar(
+  key: string,
+  options: SanitizeGitLocalEnvOptions,
+): boolean {
+  if (options.preserveGitConfigOverlay && isGitConfigOverlayEnvVar(key)) {
+    return false;
+  }
+
+  return isGitLocalEnvVar(key);
+}
+
+function isGitConfigOverlayEnvVar(key: string): boolean {
+  return (
+    key === "GIT_CONFIG_COUNT" ||
+    key === "GIT_CONFIG_PARAMETERS" ||
+    GIT_CONFIG_PAIR_ENV_VAR.test(key)
+  );
+}

src/git/environment.ts

@@ -3,6 +3,7 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 
 import type { GitleaksPluginConfig } from "../../config/index.js";
+import { sanitizeGitLocalEnv } from "../../git/environment.js";
 import type { ChangedFileResolution } from "../../path-policy/index.js";
 import {
   formatProcessFailure,
@@ -47,7 +48,7 @@ export async function runGitleaksPlugin(
       args: buildGitleaksArgs(plugin, changedFileResolution, repoRoot, reportPath),
       command: plugin.command,
       cwd: repoRoot,
-      env,
+      env: sanitizeGitLocalEnv(env),
       timeoutSeconds: plugin.timeout_seconds,
     });
 

src/runner/plugins/gitleaks.ts

@@ -1,4 +1,5 @@
 import type { ToolConfig } from "../config/index.js";
+import { sanitizeGitLocalEnv } from "../git/environment.js";
 import {
   formatProcessFailure,
   runProcessOutcome,
@@ -32,7 +33,7 @@ export async function runToolCommand(
     args,
     command: executable,
     cwd: repoRoot,
-    env,
+    env: sanitizeGitLocalEnv(env),
     timeoutSeconds: tool.timeout_seconds,
   });
 

src/runner/tool-command.ts

@@ -116,7 +116,9 @@ async function readSkipBooleanConfig(
   key: string,
 ): Promise<boolean> {
   try {
-    return await readGitBooleanConfig(repoRoot, key, env);
+    return await readGitBooleanConfig(repoRoot, key, env, {
+      preserveGitConfigOverlay: true,
+    });
   } catch (error) {
     if (error instanceof GitConfigError) {
       throw new SkipControlError(error.message);