From c8a40229dabee642d598a9a8f852e33e6a183780 Mon Sep 17 00:00:00 2001
From: Justin Worthe <justin@worthe-it.co.za>
Date: Mon, 21 Aug 2017 23:08:50 +0200
Subject: Wrote example hook for prepending branch name to file

---
 src/bin/prepare-commit-msg.rs | 57 +++++++++++++++++++++++++++++++++++++------
 1 file changed, 49 insertions(+), 8 deletions(-)

(limited to 'src/bin/prepare-commit-msg.rs')

diff --git a/src/bin/prepare-commit-msg.rs b/src/bin/prepare-commit-msg.rs
index 8118374..63edba0 100644
--- a/src/bin/prepare-commit-msg.rs
+++ b/src/bin/prepare-commit-msg.rs
@@ -1,14 +1,55 @@
+extern crate rust_git_hooks;
+
+use rust_git_hooks::*;
+use std::fs::File;
+use std::io::Write;
+use std::io::Read;
+use std::process;
 use std::env;
-use std::io::{stdin, BufRead};
 
 fn main() {
-    let args: Vec<_> = env::args().skip(1).collect();
-    println!("prepare-commit-msg called with {:?}", args);
+    log();
+
+    let current_branch = get_current_branch();
+    let commit_filename = env::args().nth(1);
 
-    println!("BEGIN STDIN for prepare-commit-msg");
-    let stdin = stdin();
-    for line in stdin.lock().lines() {
-        println!("{:?}", line);
+    
+    match (current_branch, commit_filename) {
+        (Ok(branch), Some(filename)) => {
+            let write_result = prepend_branch_name(branch, filename);
+            match write_result {
+                Ok(_) => {},
+                Err(e) => {
+                    eprintln!("Failed to prepend message. {}", e);
+                    process::exit(2);
+                }
+            };
+        },
+        (Err(e), _) => {
+            eprintln!("Failed to find current branch. {}", e);
+            process::exit(1);
+        },
+        (_, None) => {
+            eprintln!("Commit file was not provided");
+            process::exit(2);
+        }
     }
-    println!("END STDIN");
+}
+
+fn prepend_branch_name(branch_name: String, commit_filename: String) -> Result<(), std::io::Error> {
+    // It turns out that prepending a string to a file is not an
+    // obvious action. You can only write to the end of a file :(
+    //
+    // The solution is to read the existing contents, then write a new
+    // file starting with the branch name, and then writing the rest
+    // of the file.
+    
+    let mut read_commit_file = File::open(commit_filename.clone())?;
+    let mut current_message = String::new();
+    read_commit_file.read_to_string(&mut current_message)?;
+    
+    let mut commit_file = File::create(commit_filename)?;
+
+    writeln!(commit_file, "{}:", branch_name)?;
+    write!(commit_file, "{}", current_message)
 }
-- 
cgit v1.2.3