create .gitignore if not existing while `add`

This fixes a bug where the program exited when there was no existing
gitignore file.

Cargo.lock

@@ -325,7 +325,7 @@ dependencies = [
 
 [[package]]
 name = "gitig"
-version = "0.1.3"
+version = "0.1.4"
 dependencies = [
  "directories",
  "error-chain",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "gitig"
-version = "0.1.3"
+version = "0.1.4"
 authors = ["Marcel Schneider <marcel@webschneider.org>"]
 edition = "2018"
 

src/gitignore.rs

@@ -1,5 +1,6 @@
 //! This module contains an abstraction for gitignore files
 use crate::errors::*;
+use log::trace;
 use std::fs::OpenOptions;
 use std::path::PathBuf;
 
@@ -13,7 +14,10 @@ impl Gitignore {
     /// Create a new Gitignore struct from a git root folder path
     ///
     /// The given `path` must be a valid path to an existing git root folder
-    pub fn from_path(path: &PathBuf) -> Self { Gitignore { path: path.clone() } }
+    pub fn from_path(path: &PathBuf) -> Self {
+        trace!("Creating gitignore file object for path {}", path.to_string_lossy());
+        Gitignore { path: path.clone() }
+    }
 
     /// Append a line to the file
     pub fn add_line(&self, line: &str) -> Result<()> {
@@ -21,6 +25,7 @@ impl Gitignore {
         let mut file = OpenOptions::new()
             .write(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")?;