`rev-parse --show-toplevel`'s output was parsed with `first_line`, which
takes `^[^\r\n]*`. A newline is a legal byte in a POSIX path, so a
repository rooted at `/tmp/a\nb` resolved to `/tmp/a` --- and every
command afterwards ran with a `-C` and a cwd naming a directory that
does not exist, turning a working repository into a wall of exit-128
failure rows.
Fixed with a SEPARATE helper, `strip_output_terminator`, used at that
one call site. `first_line` is deliberately left alone: its other three
callers --- the spawn-error text, the stderr detail, and the
`display_file` error string --- all feed the single-line status band,
where a multi-line message corrupts the row layout, so taking the first
line is exactly right for them. Folding the two together would fix one
caller and break three. Both functions now say at their definition which
kind of text they are for and why the other exists.
Exactly one trailing newline is stripped, with an optional preceding
carriage return, because that is what git emits as a terminator; a
second newline would be output rather than a terminator. The trailing
whitespace trim `first_line` also did is NOT carried over --- a path may
legally end in a space.
Witnessed end to end by `g6_14c`, not at the parser: the fixture really
creates `<tmp>/nl\nroot`, the real `git` resolves it, and the assertion
is on the cwd of the status spawn the module actually made, plus real
rows in the panel and a RET that opens the file the row names.
Mutation-verified --- restoring `first_line` there resolves the root to
`<tmp>/nl` and fails the test.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016bqGA6s9tTUFzYpbeW3tai
Levi Neuwirth
842ec61f6f