Function spawn_editor 

pub fn spawn_editor(template: &str) -> Result<String>

Spawn the user’s editor on a tempfile pre-populated with template, then read the file back, strip #-comment lines, and return the trimmed result.

The editor is chosen in this order:

1. $GIT_EDITOR
2. $EDITOR
3. $VISUAL
4. platform default (vi on Unix, notepad on Windows)

The editor invocation parses the chosen value as a shell-like command: the first whitespace-separated token is the program, the rest are arguments, and the tempfile path is appended as a final argument. This matches how git’s GIT_EDITOR is conventionally parsed (e.g. EDITOR="vim -c 'set nowrap'").

Errors

• io::ErrorKind::NotFound if the editor binary cannot be spawned.
• io::ErrorKind::Other with a descriptive message if the editor exits non-zero or the file exceeds MAX_COMMIT_MSG_BYTES.