Abort fix with changes in working directory

docs/src/cli/usage.md

@@ -9,7 +9,7 @@ USAGE:
 FLAGS:
         --allow-warnings    Pass when only warnings occur
         --no-exclude        Ignore excludes defined in config
-        --fix               Automatically applies some lint suggestions
+        --fix               Automatically fix applicable lint warnings
     -h, --help              Prints help information
     -n, --no-summary        Suppress summary information
     -q, --quiet             Display only the necessary information. Equivalent to --display-style="quiet"

selene/src/main.rs

@@ -3,6 +3,7 @@ use std::{
     fmt, fs,
     io::{self, Read, Write},
     path::{Path, PathBuf},
+    process::Command,
     sync::{
         atomic::{AtomicUsize, Ordering},
         Arc, RwLock,
@@ -664,6 +665,16 @@ fn start(mut options: opts::Options) {
 
     let pool = ThreadPool::new(options.num_threads);
 
+    if options.fix && !options.allow_dirty {
+        if has_unstaged_changes() || (!options.allow_staged && has_staged_changes()) {
+            error(
+                "the working directory of this package has uncommitted changes, and `cargo fix`
+                can potentially perform destructive changes; if you'd like to suppress this error pass
+                `--allow-dirty`, `--allow-staged`, or commit the changes to these"
+            );
+        }
+    }
+
     for filename in &options.files {
         if filename == "-" {
             let checker = Arc::clone(&checker);
@@ -830,6 +841,30 @@ fn get_opts_safe(mut args: Vec<OsString>, luacheck: bool) -> Result<opts::Option
     }
 }
 
+fn has_unstaged_changes() -> bool {
+    let output = Command::new("git")
+        .arg("status")
+        .arg("--porcelain")
+        .output()
+        .expect("Failed to execute git");
+
+    let stdout = String::from_utf8(output.stdout).expect("Failed to convert git output to string");
+
+    stdout.lines().any(|line| line.chars().nth(1) != Some(' '))
+}
+
+fn has_staged_changes() -> bool {
+    let output = Command::new("git")
+        .arg("status")
+        .arg("--porcelain")
+        .output()
+        .expect("Failed to execute git");
+
+    let stdout = String::from_utf8(output.stdout).expect("Failed to convert git output to string");
+
+    stdout.lines().any(|line| line.chars().nth(0) != Some(' '))
+}
+
 #[cfg(feature = "roblox")]
 fn generate_roblox_std() -> color_eyre::Result<StandardLibrary> {
     let (contents, std) = roblox::RobloxGenerator::generate()?;

selene/src/opts.rs

@@ -72,6 +72,16 @@ pub struct Options {
 
     #[structopt(long)]
     pub fix: bool,
+
+    // Fix code even if the working directory has changes
+    // Only used with `fix`
+    #[structopt(long, hidden(true))]
+    pub allow_dirty: bool,
+
+    // Fix code even if the working directory has staged changes
+    // Only used with `fix`
+    #[structopt(long, hidden(true))]
+    pub allow_staged: bool,
 }
 
 impl Options {