Respect GIT_DIR set by git (#1258)

* Respect `GIT_DIR` set by git

* test

* Set GIT_WORK_TREE

* Add test

crates/prek-consts/src/env_vars.rs

@@ -10,6 +10,8 @@ impl EnvVars {
     pub const CI: &'static str = "CI";
 
     // Git related
+    pub const GIT_DIR: &'static str = "GIT_DIR";
+    pub const GIT_WORK_TREE: &'static str = "GIT_WORK_TREE";
     pub const GIT_TERMINAL_PROMPT: &'static str = "GIT_TERMINAL_PROMPT";
 
     pub const SKIP: &'static str = "SKIP";

crates/prek/src/cli/install.rs

@@ -286,18 +286,12 @@ fn install_hook_script(
 
 /// The version of the hook script. Increment this when the script changes in a way that
 /// requires re-installation.
-pub(crate) static CUR_SCRIPT_VERSION: usize = 3;
+pub(crate) static CUR_SCRIPT_VERSION: usize = 4;
 
 static HOOK_TMPL: &str = r#"[SHEBANG]
 # File generated by prek: https://github.com/j178/prek
 # ID: 182c10f181da4464a3eec51b83331688
 
-# Unset GIT_DIR to avoid git taking current directory as the git dir.
-# See:
-# https://github.com/pre-commit/pre-commit/issues/2295
-# https://www.spinics.net/lists/git/msg374197.html
-unset GIT_DIR
-
 ARGS=([PREK_ARGS])
 
 HERE="$(cd "$(dirname "$0")" && pwd)"

crates/prek/src/main.rs

@@ -9,6 +9,7 @@ use anyhow::{Context, Result};
 use clap::{CommandFactory, Parser};
 use clap_complete::CompleteEnv;
 use owo_colors::OwoColorize;
+use prek_consts::env_vars::EnvVars;
 use tracing::debug;
 use tracing::level_filters::LevelFilter;
 use tracing_subscriber::filter::Directive;
@@ -137,7 +138,7 @@ fn setup_logging(level: Level, log_file: LogFile, store: &Store) -> Result<()> {
     Ok(())
 }
 
-async fn run(mut cli: Cli) -> Result<ExitStatus> {
+async fn run(cli: Cli) -> Result<ExitStatus> {
     // Enabled ANSI colors on Windows.
     let _ = anstyle_query::windows::enable_ansi_colors();
 
@@ -175,12 +176,24 @@ async fn run(mut cli: Cli) -> Result<ExitStatus> {
         warnings::enable();
     }
 
-    if cli.command.is_none() {
-        cli.command = Some(Command::Run(Box::new(cli.run_args.clone())));
-    }
-
     debug!("prek: {}", version::version());
 
+    // If `GIT_DIR` is set, prek may be running from a git hook.
+    // Git exports `GIT_DIR` but *not* `GIT_WORK_TREE`. Without `GIT_WORK_TREE`, git
+    // treats the current working directory as the working tree. If prek changes the current
+    // working directory (with `--cd`), git commands run by prek may behave unexpectedly.
+    //
+    // To make git behavior stable, we set `GIT_WORK_TREE` ourselves to where prek is run from.
+    // If `GIT_WORK_TREE` is already set, we leave it alone.
+    // If `GIT_DIR` is not set, we let git discover `.git` after an optional `cd`.
+    // See: https://www.spinics.net/lists/git/msg374197.html
+    //      https://github.com/pre-commit/pre-commit/issues/2295
+    if EnvVars::is_set(EnvVars::GIT_DIR) && !EnvVars::is_set(EnvVars::GIT_WORK_TREE) {
+        let cwd = std::env::current_dir().context("Failed to get current directory")?;
+        debug!("Setting {} to `{}`", EnvVars::GIT_WORK_TREE, cwd.display());
+        unsafe { std::env::set_var(EnvVars::GIT_WORK_TREE, cwd) }
+    }
+
     if let Some(dir) = cli.globals.cd.as_ref() {
         debug!("Changing current directory to: `{}`", dir.display());
         std::env::set_current_dir(dir)?;
@@ -203,7 +216,10 @@ async fn run(mut cli: Cli) -> Result<ExitStatus> {
     }
     show_settings!(cli.globals, false);
 
-    match cli.command.unwrap() {
+    let command = cli
+        .command
+        .unwrap_or_else(|| Command::Run(Box::new(cli.run_args)));
+    match command {
         Command::Install(args) => {
             show_settings!(args);
 

crates/prek/tests/hook_impl.rs

@@ -1,9 +1,10 @@
+use std::process::Command;
+
 use assert_cmd::assert::OutputAssertExt;
 use assert_fs::fixture::{FileWriteStr, PathChild, PathCreateDir};
 use indoc::indoc;
 use prek_consts::CONFIG_FILE;
 use prek_consts::env_vars::EnvVars;
-use std::process::Command;
 
 use crate::common::TestContext;
 use crate::common::cmd_snapshot;
@@ -187,6 +188,8 @@ fn hook_impl_pre_push() -> anyhow::Result<()> {
 fn run_worktree() -> anyhow::Result<()> {
     let context = TestContext::new();
     context.init_project();
+    context.configure_git_author();
+    context.disable_auto_crlf();
     context.write_pre_commit_config(indoc! { r"
         repos:
         - repo: local
@@ -197,8 +200,6 @@ fn run_worktree() -> anyhow::Result<()> {
              entry: always fail
              always_run: true
     "});
-    context.configure_git_author();
-    context.disable_auto_crlf();
     context.git_add(".");
     context.git_commit("Initial commit");
 
@@ -249,6 +250,61 @@ fn run_worktree() -> anyhow::Result<()> {
     Ok(())
 }
 
+/// Test prek hooks runs with `GIT_DIR` respected.
+#[test]
+fn git_dir_respected() {
+    let context = TestContext::new();
+    context.init_project();
+    context.configure_git_author();
+    context.disable_auto_crlf();
+    context.write_pre_commit_config(indoc! { r#"
+        repos:
+        - repo: local
+          hooks:
+           - id: print-git-dir
+             name: Print Git Dir
+             language: python
+             entry: python -c 'import os, sys; print("GIT_DIR:", os.environ.get("GIT_DIR")); print("GIT_WORK_TREE:", os.environ.get("GIT_WORK_TREE")); sys.exit(1)'
+             pass_filenames: false
+    "#});
+    context.git_add(".");
+    let cwd = context.work_dir();
+
+    cmd_snapshot!(context.filters(), context.install(), @r#"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    prek installed at `.git/hooks/pre-commit`
+
+    ----- stderr -----
+    "#);
+
+    let mut commit = Command::new("git");
+    commit
+        .arg("--git-dir")
+        .arg(cwd.join(".git"))
+        .arg("--work-tree")
+        .arg(&**cwd)
+        .current_dir(context.home_dir())
+        .arg("commit")
+        .arg("-m")
+        .arg("Test commit with GIT_DIR set");
+
+    cmd_snapshot!(context.filters(), commit, @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+    Print Git Dir............................................................Failed
+    - hook id: print-git-dir
+    - exit code: 1
+
+      GIT_DIR: [TEMP_DIR]/.git
+      GIT_WORK_TREE: .
+    ");
+}
+
 #[test]
 fn workspace_hook_impl_root() -> anyhow::Result<()> {
     let context = TestContext::new();
@@ -455,6 +511,7 @@ fn workspace_hook_impl_worktree_subdirectory() -> anyhow::Result<()> {
     let mut commit = Command::new("git");
     commit
         .current_dir(cwd.child("worktree"))
+        .env(EnvVars::PREK_HOME, &**context.home_dir())
         .arg("commit")
         .arg("-m")
         .arg("Test commit from subdirectory")
@@ -494,14 +551,14 @@ fn workspace_hook_impl_no_project_found() -> anyhow::Result<()> {
     context.git_add(".");
 
     // Install hook that allows missing config
-    cmd_snapshot!(context.filters(), context.install(), @r#"
+    cmd_snapshot!(context.filters(), context.install(), @r"
     success: true
     exit_code: 0
     ----- stdout -----
     prek installed at `.git/hooks/pre-commit`
 
     ----- stderr -----
-    "#);
+    ");
 
     // Try to run hook-impl from directory without config
     let mut commit = Command::new("git");

crates/prek/tests/install.rs

@@ -38,13 +38,7 @@ fn install() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -84,13 +78,7 @@ fn install() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -119,13 +107,7 @@ fn install() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=post-commit --script-version=3)
+            ARGS=(hook-impl --hook-type=post-commit --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -162,13 +144,7 @@ fn install() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -191,13 +167,7 @@ fn install() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=post-commit --script-version=3)
+            ARGS=(hook-impl --hook-type=post-commit --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -269,13 +239,7 @@ fn install_with_hooks() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -450,13 +414,7 @@ fn init_template_dir() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --skip-on-missing-config --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --skip-on-missing-config --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -493,13 +451,7 @@ fn init_template_dir() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --skip-on-missing-config --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --skip-on-missing-config --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -533,13 +485,7 @@ fn init_template_dir() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --config="non-exist-config" --skip-on-missing-config --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --config="non-exist-config" --skip-on-missing-config --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -639,13 +585,7 @@ fn workspace_install() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -682,13 +622,7 @@ fn workspace_install() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --cd="project3" --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --cd="project3" --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -722,13 +656,7 @@ fn workspace_install() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl project3/ --skip=project2/ --hook-type=pre-commit --script-version=3)
+            ARGS=(hook-impl project3/ --skip=project2/ --hook-type=pre-commit --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -774,13 +702,7 @@ fn workspace_install() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl project3/ --hook-type=pre-commit --script-version=3)
+            ARGS=(hook-impl project3/ --hook-type=pre-commit --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")
@@ -1005,13 +927,7 @@ fn workspace_init_template_dir() -> anyhow::Result<()> {
             # File generated by prek: https://github.com/j178/prek
             # ID: 182c10f181da4464a3eec51b83331688
 
-            # Unset GIT_DIR to avoid git taking current directory as the git dir.
-            # See:
-            # https://github.com/pre-commit/pre-commit/issues/2295
-            # https://www.spinics.net/lists/git/msg374197.html
-            unset GIT_DIR
-
-            ARGS=(hook-impl --hook-type=pre-commit --skip-on-missing-config --script-version=3)
+            ARGS=(hook-impl --hook-type=pre-commit --skip-on-missing-config --script-version=4)
 
             HERE="$(cd "$(dirname "$0")" && pwd)"
             ARGS+=(--hook-dir "$HERE" -- "$@")

crates/prek/tests/run.rs

@@ -2040,6 +2040,7 @@ fn git_commit_a() -> Result<()> {
         .arg("-a")
         .arg("-m")
         .arg("Update file")
+        .env(EnvVars::PREK_HOME, &**context.home_dir())
         .current_dir(cwd);
 
     let filters = context