Add handling of files with missing newline at end

src/app.rs

@@ -107,7 +107,10 @@ fn add(glob: &str, local: bool) -> Result<()> {
     info!("Working with git root in {:?}", root);
 
     let mut file_path = PathBuf::from(&root);
-    if local {
+    let override_path = std::env::var("GITIG_OVERRIDE_PATH").ok();
+    if let Some(override_path) = override_path {
+        file_path = PathBuf::from(override_path);
+    } else if local {
         file_path.push(".git/info/exclude")
     } else {
         file_path.push(".gitignore");

src/gitignore.rs

@@ -28,7 +28,6 @@ impl Gitignore {
     /// # Errors
     ///
     /// - `ErrorKind::NoGitRootFound` when there was .gitignore file found at the default location
-    ///
     pub fn from_default_path() -> Result<Self> {
         let mut path = git_dir()?.ok_or(ErrorKind::NoGitRootFound)?;
         path.push(".gitignore");
@@ -40,11 +39,30 @@ impl Gitignore {
         use std::io::prelude::*;
         let mut file = OpenOptions::new()
             .write(true)
+            .read(true)
             .append(true)
             .create(true)
             .open(&self.path)
             .chain_err(|| "Error while opening gitignore file")?;
-        writeln!(file, "{}", line).chain_err(|| "Error while writing line to gitignore")?;
+
+        let file_len = file.stream_len()?;
+        let newline = if file_len > 0 {
+            file.seek(std::io::SeekFrom::End(-1))?;
+            let mut buf: Vec<u8> = vec![0; 1];
+            file.read_exact(&mut buf)?;
+            if buf[0] == '\n' as u8 {
+                // The last line already ends with a newline
+                ""
+            } else {
+                // Add a newline if the last line doesn't end with one
+                "\n"
+            }
+        } else {
+            // The file is empty, so we don't need a newline
+            ""
+        };
+        writeln!(file, "{}{}", newline, line)
+            .chain_err(|| "Error while writing line to gitignore")?;
         Ok(())
     }
 

src/main.rs

@@ -29,6 +29,7 @@ This project used [rust-cli-boilerplate](https://github.com/ssokolow/rust-cli-bo
     clippy::wildcard_imports,
     clippy::integer_arithmetic
 )]
+#![feature(seek_stream_len)]
 
 #[macro_use]
 extern crate error_chain;