Fix git-lfs not found in Flatpak build

Closes #180

Author: pol-rivero

README.md

@@ -260,6 +260,9 @@ Simply install GitHub Desktop Plus from [Flathub](https://flathub.org/en/apps/io
 flatpak install flathub io.github.pol_rivero.github-desktop-plus
 ```
 
+> **NOTE:** Git hooks will run inside the Flatpak sandbox and cannot access programs installed on your system (such as version managers,
+> linters, or other tools your hooks rely on). If your hooks depend on such programs, install a native package instead.
+
 ---
 
 </details>

app/src/lib/hooks/hooks-proxy.ts

@@ -2,7 +2,7 @@ import { spawn } from 'child_process'
 import { basename, resolve, join } from 'path'
 import { ProcessProxyConnection as Connection } from 'process-proxy'
 import type { HookCallbackOptions } from '../git'
-import { resolveGitBinary } from 'dugite'
+import { resolveGitBinary, resolveGitExecPath } from 'dugite'
 import { ShellEnvResult } from './get-shell-env'
 import { shellFriendlyNames } from './config'
 import { Writable } from 'stream'
@@ -145,7 +145,9 @@ export const createHooksProxy = (
     ]
 
     const terminalOutput: Buffer[] = []
-    const gitPath = resolveGitBinary(resolve(__dirname, 'git'))
+    const gitDir = resolve(__dirname, 'git')
+    const gitPath = resolveGitBinary(gitDir)
+    const gitExecPath = resolveGitExecPath(gitDir)
     const shellEnv = await getShellEnv(proxyCwd)
 
     if (shellEnv.kind === 'failure') {
@@ -174,9 +176,20 @@ export const createHooksProxy = (
 
       const child = spawn(gitPath, args, {
         cwd: proxyCwd,
-        // GITHUB_DESKTOP lets hooks know they're run from GitHub Desktop.
-        // See https://github.com/desktop/desktop/issues/19001
-        env: { ...shellEnv.env, ...safeEnv, GITHUB_DESKTOP: '1' },
+        env: {
+          ...shellEnv.env,
+          ...safeEnv,
+          // The bundled Git can't resolve its own exec-path when spawned this
+          // way (it reports "//libexec/git-core"), so set it explicitly. Native
+          // Git prepends GIT_EXEC_PATH to the hook's PATH, which is what makes
+          // the bundled git-lfs (and git) findable from inside the hook. This
+          // matters most in sandboxed builds (e.g. Flatpak) where no system
+          // git-lfs exists on PATH to fall back on.
+          GIT_EXEC_PATH: gitExecPath,
+          // GITHUB_DESKTOP lets hooks know they're run from GitHub Desktop.
+          // See https://github.com/desktop/desktop/issues/19001
+          GITHUB_DESKTOP: '1',
+        },
         signal: abortController.signal,
       })
         .on('close', (code, signal) => resolve({ code, signal }))

app/src/ui/preferences/git.tsx

@@ -83,6 +83,20 @@ export class Git extends React.Component<IGitProps> {
   private renderHooksSettings() {
     return (
       <>
+        {__FLATPAK__ && (
+          <div className="git-hooks-flatpak-warning">
+            <span className="warning-icon">⚠️</span>
+            You're running the Flatpak version. Git hooks run inside the Flatpak
+            sandbox and cannot access programs installed on your system (such as
+            version managers, linters, or other tools your hooks rely on). If
+            your hooks depend on such programs, install a native package
+            instead. See the{' '}
+            <LinkButton uri="https://github.com/pol-rivero/github-desktop-plus#download-and-installation-">
+              installation instructions
+            </LinkButton>
+            .
+          </div>
+        )}
         <Checkbox
           label="Load Git hook environment variables from shell"
           ariaDescribedBy="git-hooks-env-description"

app/styles/_ui.scss

@@ -105,6 +105,7 @@
 @import 'ui/_pull-request-quick-view';
 @import 'ui/discard-changes-retry';
 @import 'ui/_git-email-not-found-warning';
+@import 'ui/_git-hooks-flatpak-warning';
 @import 'ui/_branch-select';
 @import 'ui/_popover-dropdown';
 @import 'ui/_pull-request-files-changed';

app/styles/ui/_git-hooks-flatpak-warning.scss

@@ -0,0 +1,11 @@
+.git-hooks-flatpak-warning {
+  .warning-icon {
+    color: var(--warning-badge-icon-color);
+  }
+
+  .link-button-component {
+    display: inline;
+  }
+
+  margin-bottom: var(--spacing-double);
+}