An quick program for parsing `git log` output and capturing each commit's hash and commit message.

parsing-subprocess-output.rs

#[macro_use]
extern crate error_chain;
extern crate regex;

use std::process::Command;
use regex::Regex;

error_chain!{
    foreign_links {
        Io(std::io::Error);
        Regex(regex::Error);
        Utf8(std::string::FromUtf8Error);
    }
}


#[derive(PartialEq, Default, Clone, Debug)]
struct Commit {
    hash: String,
    message: String,
}


fn run() -> Result<()> {
    let output = Command::new("git").arg("log").arg("--oneline").output()?;

    if !output.status.success() {
        bail!("Command executed with failing error code");
    }

    let pattern = Regex::new(r"(?x)
                               ([0-9a-fA-F]+) # commit hash
                               (.*)           # The commit message")?;

    let stdout = String::from_utf8(output.stdout)?;
    let commits = stdout
        .lines()
        .filter_map(|line| pattern.captures(line))
        .map(|cap| {
                 Commit {
                     hash: cap[1].to_string(),
                     message: cap[2].trim().to_string(),
                 }
             });

    for commit in commits {
        println!("{:?}", commit);
    }

    Ok(())
}

quick_main!(run);

Running this on my fork of rust-cookbook gives the following output:

$ cd ~/Documents/forks/rust-cookbook && /tmp/parsing-subprocess-output | head
Commit { hash: "fd0e0b4", message: "Merge pull request #120 from gsquire/head-example" }
Commit { hash: "bbfdc8a", message: "remove dead link" }
Commit { hash: "3cd5ab1", message: "update some of the wording to be clearer" }
Commit { hash: "761054f", message: "add an example for making a HEAD request with a timeout" }
Commit { hash: "4a5c675", message: "Add CI badge to readme" }
Commit { hash: "2dcc48b", message: "Merge pull request #118 from budziq/label_sync" }
Commit { hash: "ed3a42d", message: "Travis \"cron\" builds run tests with \"*\" dependencies" }
Commit { hash: "62fd9dc", message: "Link to example of a commit" }
Commit { hash: "e698443", message: "Add percent-encode example" }
Commit { hash: "cbad25c", message: "Sort badge links" }

And the original command's output:

$ git log --oneline | head
fd0e0b4 Merge pull request #120 from gsquire/head-example
bbfdc8a remove dead link
3cd5ab1 update some of the wording to be clearer
761054f add an example for making a HEAD request with a timeout
4a5c675 Add CI badge to readme
2dcc48b Merge pull request #118 from budziq/label_sync
ed3a42d Travis "cron" builds run tests with "*" dependencies
62fd9dc Link to example of a commit
e698443 Add percent-encode example
cbad25c Sort badge links