git_blamediff/
lib.rs

1// Copyright (C) 2022 Daniel Mueller <deso@posteo.net>
2// SPDX-License-Identifier: GPL-3.0-or-later
3
4use std::env::Args;
5use std::ffi::OsStr;
6use std::io::stdout;
7use std::io::BufRead as _;
8use std::io::BufReader;
9use std::io::Error;
10use std::io::ErrorKind;
11use std::io::Result;
12use std::io::Write as _;
13use std::ops::Deref as _;
14use std::process::Child;
15use std::process::ChildStdout;
16use std::process::Command;
17use std::process::Stdio;
18
19use diff_parse::File;
20
21
22/// The path to the `git` binary used by default.
23pub const GIT: &str = "/usr/bin/git";
24
25
26/// Wait for a child process to finish and map failures to an
27/// appropriate error.
28pub fn await_child<S>(program: S, child: Child) -> Result<Option<ChildStdout>>
29where
30  S: AsRef<OsStr>,
31{
32  let mut child = child;
33
34  let status = child.wait()?;
35  if !status.success() {
36    let error = format!("process `{}` failed", program.as_ref().to_string_lossy());
37
38    if let Some(stderr) = child.stderr {
39      let mut stderr = BufReader::new(stderr);
40      let mut line = String::new();
41
42      // Let's try to include the first line of the error output in our
43      // error, to at least give the user something.
44      if stderr.read_line(&mut line).is_ok() {
45        let line = line.trim();
46        return Err(Error::new(ErrorKind::Other, format!("{error}: {line}")))
47      }
48    }
49    return Err(Error::new(ErrorKind::Other, error))
50  }
51  Ok(child.stdout)
52}
53
54
55/// Invoke git to annotate all the diff hunks.
56// TODO: For some reason `ArgsOs` is not `Clone`, which is why we pass
57//       in a function that recreates such an object every time.
58pub fn blame<A>(diffs: &[(File, File)], args: A) -> Result<()>
59where
60  A: Fn() -> Args,
61{
62  let out = stdout();
63  let mut out = out.lock();
64
65  for (src, dst) in diffs {
66    // Start off by printing some information on the file we are
67    // currently annotating.
68    // TODO: We should print the file header only once.
69    writeln!(out, "--- {}", src.file)?;
70    writeln!(out, "+++ {}", dst.file)?;
71    // Make sure stdout is flushed properly before invoking a git command
72    // to be sure our output arrives before that of git.
73    let () = out.flush()?;
74
75    // Invoke git with the appropriate options to annotate the lines of
76    // the diff.
77    // TODO: Make the arguments here more configurable. In fact, we
78    //       should not hard-code any of them here.
79    let child = Command::new(GIT)
80      .arg("--no-pager")
81      .arg("blame")
82      .arg("-s")
83      .arg(format!("-L{},+{}", src.line, src.count))
84      .args(args().skip(1))
85      .arg("--")
86      .arg(src.file.deref())
87      .arg("HEAD")
88      .stdin(Stdio::null())
89      .stdout(Stdio::inherit())
90      .stderr(Stdio::piped())
91      .spawn()?;
92    let _ = await_child(GIT, child)?;
93  }
94  Ok(())
95}
git_blamediff/lib.rs

git_blamediff/
lib.rs
