Function parse 

pub fn parse(report: &str) -> Option<GitWorkingTree>

Parse a git status --porcelain=v2 --branch -z report.

Records are NUL-separated. A rename record (2 ) carries two NUL-separated paths, so the parser consumes one extra record after it; a parser that does not is silently one record out of step for the rest of the report, which is the classic way this format is got wrong.

use majordomus_cli::environment::vcs::parse;
// One record per entry, joined by the NUL the report separates them with.
let report = [
    "# branch.oid abc123",
    "# branch.head master",
    "# branch.upstream origin/master",
    "# branch.ab +2 -1",
    "1 .M N... 100644 100644 100644 aaa bbb src/a.rs",
    "1 M. N... 100644 100644 100644 ccc ddd src/b.rs",
    "? notes.txt",
].join("\0");
let tree = parse(&report).expect("a branch header");
assert_eq!(tree.branch.as_deref(), Some("master"));
assert_eq!(tree.upstream.as_deref(), Some("origin/master"));
assert_eq!((tree.ahead, tree.behind), (Some(2), Some(1)));
assert_eq!((tree.staged, tree.modified, tree.untracked), (1, 1, 1));
assert!(!tree.clean);