Add `cat` command

Fixes #5

src/app.rs

@@ -65,7 +65,7 @@ pub enum Command {
     /// Add a line to the gitignore
     Add {
         /// The glob string that should be added
-        glob:  Vec<String>,
+        glob: Vec<String>,
         /// Add the entry to the repo local ignore file
         #[structopt(short)]
         local: bool,
@@ -78,7 +78,7 @@ pub enum Command {
         /// The language for which the gitignore should be downloaded
         ///
         /// A list with all available languages and projects can be printed with `list-templates`.
-        lang:   String,
+        lang: String,
     },
     /// List all available templates that can be downloaded
     ListTemplates,
@@ -87,6 +87,8 @@ pub enum Command {
         /// Shell to generate completion for
         shell: Option<structopt::clap::Shell>,
     },
+    /// Print current .gitignore to stdout
+    Cat,
 }
 
 /// Runs the command `add`
@@ -168,6 +170,15 @@ fn run_dump_completion(shell: Option<structopt::clap::Shell>) -> Result<()> {
     Ok(())
 }
 
+/// Runs the `cat` command to print the contents
+fn run_cat() -> Result<()> {
+    let ignore_file = Gitignore::from_default_path()?;
+    let mut buf = String::new();
+    ignore_file.contents(&mut buf)?;
+    println!("{}", buf);
+    Ok(())
+}
+
 /// The actual `main()`
 pub fn main(opts: CliOpts) -> Result<()> {
     match opts.cmd {
@@ -175,6 +186,7 @@ pub fn main(opts: CliOpts) -> Result<()> {
         Command::Get { lang, append } => run_get(&lang, append)?,
         Command::ListTemplates => run_list_templates()?,
         Command::DumpCompletions { shell } => run_dump_completion(shell)?,
+        Command::Cat => run_cat()?,
     };
 
     Ok(())

src/gitignore.rs

@@ -1,5 +1,6 @@
 //! This module contains an abstraction for gitignore files
 use crate::errors::*;
+use crate::helpers::git_dir;
 use log::trace;
 use std::fs::OpenOptions;
 use std::path::PathBuf;
@@ -19,6 +20,21 @@ impl Gitignore {
         Gitignore { path: path.clone() }
     }
 
+    /// Return a new `Gitignore` object from the default location
+    ///
+    /// This function gets the default .gitignore in the git root folder for the current working
+    /// directory
+    ///
+    /// # 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");
+        Ok(Self::from_path(&path))
+    }
+
     /// Append a line to the file
     pub fn add_line(&self, line: &str) -> Result<()> {
         use std::io::prelude::*;
@@ -31,6 +47,17 @@ impl Gitignore {
         writeln!(file, "{}", line).chain_err(|| "Error while writing line to gitignore")?;
         Ok(())
     }
+
+    /// Reads the contents of the gitignore file and adds them to buf
+    pub fn contents(&self, buf: &mut String) -> Result<()> {
+        use std::io::prelude::*;
+        let mut file = OpenOptions::new()
+            .read(true)
+            .open(&self.path)
+            .chain_err(|| "Error while opening gitignore file")?;
+        file.read_to_string(buf)?;
+        Ok(())
+    }
 }
 
 impl std::fmt::Display for Gitignore {